1. For Desktop Audio capture, that's because Apple (the creator of OSX/MacOS) doesn't want you to be able to capture it, so you should complain at them for going out of their way to keep you from doing what you want.
2. You didn't post a log, so I can't comment on why you would need a 3rd party program to capture your mic, but I can say that every mic source/type that I have tested works just as well (or poorly) on Windows as MacOS natively (i.e. no 3rd party program required). If you can post a log and wish to elaborate on this point we can try to help you or maybe fix/resolve it.
3. Some programs choose to display their interface in a different manner then 'normal' programs. It's mostly content-creation programs that choose to draw themselves this way (for performance reasons)...and when they do that Window capture doesn't work. That's why you have to use Display capture. This is true on both Windows and MacOS.
(For the record, try Window capturing PS, AI, AE, PSP, Sai or Premiere on Windows with OBS. You have to use Display capture for those, because Window capture doesn't work, same as MacOS).
To be brutally honest, I would say that your complaint about OBS not being as great on MacOS as Windows, while technically true, is ultimately pointless. Every difference between the Windows and MacOS versions exist because of you choosing to go with a OS/company (MacOS/Apple) that goes out of their way to only allow you to do things they think you should be allowed to do.
I could give example after example of the amount of time spent (personally I would say wasted) on coding workarounds for Apple and their silliness, time that could have been spent on making OBS a better program overall.
So please keep that in mind when complaining about OBS not being as good on MacOS as on Windows, and instead direct your complaints at the company causing you these issues: Apple.
LOG
07:41:53.622: CPU Name: Intel(R) Core(TM) i7-4850HQ CPU @ 2.30GHz
07:41:53.622: CPU Speed: 2300MHz
07:41:53.622: Physical Cores: 4, Logical Cores: 8
07:41:53.622: Physical Memory: 16384MB Total
07:41:53.622: OS Name: Mac OS X (NSMACHOperatingSystem)
07:41:53.622: OS Version: Version 10.12.4 (Build 16E195)
07:41:53.622: Kernel Version: 16.5.0
07:41:53.631: hotkeys-cocoa: Using layout 'com.apple.keylayout.US'
07:41:54.052: OBS 0.16.2 (mac)
07:41:54.052: ---------------------------------
07:41:54.052: ---------------------------------
07:41:54.052: audio settings reset:
07:41:54.052: samples per sec: 44100
07:41:54.052: speakers: 2
07:41:54.220: ---------------------------------
07:41:54.220: video settings reset:
07:41:54.220: base resolution: 1920x1200
07:41:54.220: output resolution: 1920x1200
07:41:54.220: downscale filter: Bilinear
07:41:54.220: fps: 30/1
07:41:54.220: format: RGBA
07:41:54.220: GPU conversion not available for format: 6
07:41:54.220: ---------------------------------
07:41:54.450: No blackmagic support
07:41:54.581: [VideoToolbox encoder]: Adding VideoToolbox H264 encoders
07:41:54.857: os_dlopen(/Applications/VLC.app/Contents/MacOS/lib/libvlc.5.dylib->/Applications/VLC.app/Contents/MacOS/lib/libvlc.5.dylib): dlopen(/Applications/VLC.app/Contents/MacOS/lib/libvlc.5.dylib, 1): image not found
07:41:54.857:
07:41:54.857: Couldn't find VLC installation, VLC video source disabled
07:41:54.892: Failed to load 'en-US' text for module: 'obs-browser.so'
07:41:54.892: [browser_source: 'Version: 1.25.0']
07:41:54.892: ---------------------------------
07:41:54.892: Loaded Modules:
07:41:54.892: obs-browser.so
07:41:54.892: vlc-video.so
07:41:54.892: text-freetype2.so
07:41:54.892: rtmp-services.so
07:41:54.892: obs-x264.so
07:41:54.892: obs-transitions.so
07:41:54.892: obs-outputs.so
07:41:54.892: obs-filters.so
07:41:54.892: obs-ffmpeg.so
07:41:54.892: mac-vth264.so
07:41:54.892: mac-syphon.so
07:41:54.892: mac-decklink.so
07:41:54.892: mac-capture.so
07:41:54.892: mac-avcapture.so
07:41:54.892: image-source.so
07:41:54.892: frontend-tools.so
07:41:54.892: coreaudio-encoder.so
07:41:54.892: ==== Startup complete ===============================================
07:41:55.475: All scene data cleared
07:41:55.475: ------------------------------------------------
07:41:55.541: coreaudio: device 'Soundflower (2ch)' initialized
07:41:55.544: coreaudio: device 'Built-in Microphone' initialized
07:41:55.545: [Media Source 'Intermission Video']: invalid audio_buffer_size 1
07:41:55.545: [Media Source 'Intermission Video']: invalid audio_buffer_size 1
07:41:55.545: [Media Source 'Intermission Video']: settings:
07:41:55.545: input: /Users/alikemiller/Library/Mobile Documents/com~apple~CloudDocs/RYUU GIRL - COMPANY/COMPANY VIDEOS/intermission screen.mp4
07:41:55.545: input_format: (null)
07:41:55.545: is_looping: no
07:41:55.545: is_forcing_scale: yes
07:41:55.545: is_hw_decoding: yes
07:41:55.545: is_clear_on_media_end: yes
07:41:55.545: restart_on_activate: yes
07:41:55.545: [Media Source 'Intermission Video']: advanced settings:
07:41:55.545: audio_buffer_size: 1
07:41:55.545: video_buffer_size: 1
07:41:55.545: frame_drop: AVDISCARD_DEFAULT
07:41:55.558: FT2-text: Failed to open /Users/alikemiller/Documents/RYUU GIRL - COMPANY/Stream Labs/all_time_top_donator.txt for reading
07:41:55.676: adding 23 milliseconds of audio buffering, total audio buffering is now 23 milliseconds
07:41:55.798: adding 23 milliseconds of audio buffering, total audio buffering is now 46 milliseconds
07:41:56.295: Webcam: Selected device 'FaceTime HD Camera'
07:41:56.299: Webcam: Using preset 960x540
07:41:56.828: Switched to scene 'Twitch'
07:41:56.828: ------------------------------------------------
07:41:56.828: Loaded scenes:
07:41:56.828: - scene 'Intermission':
07:41:56.828: - source: 'Intermission Video' (ffmpeg_source)
07:41:56.828: - scene 'Twitch':
07:41:56.876: - source: 'AI' (window_capture)
07:41:56.876: - source: 'DESKTOP' (display_capture)
07:41:56.876: - source: 'CLIP STUDIO PAINT' (window_capture)
07:41:56.876: - source: 'Webcam' (av_capture_input)
07:41:56.876: - source: 'AE' (window_capture)
07:41:56.876: - source: 'OVERLAY' (image_source)
07:41:56.876: - source: 'Alert Box' (browser_source)
07:41:56.876: - source: 'Donation Ticker' (browser_source)
07:41:56.876: - source: 'Top Donor' (text_ft2_source)
07:41:56.876: - source: 'Event List' (browser_source)
07:41:56.876: ------------------------------------------------
07:44:09.353: adding 23 milliseconds of audio buffering, total audio buffering is now 69 milliseconds
07:44:09.381: adding 23 milliseconds of audio buffering, total audio buffering is now 92 milliseconds
07:44:09.408: adding 23 milliseconds of audio buffering, total audio buffering is now 116 milliseconds
07:44:09.435: adding 23 milliseconds of audio buffering, total audio buffering is now 139 milliseconds
07:44:09.461: adding 23 milliseconds of audio buffering, total audio buffering is now 162 milliseconds
07:44:09.486: adding 23 milliseconds of audio buffering, total audio buffering is now 185 milliseconds
07:44:09.510: adding 23 milliseconds of audio buffering, total audio buffering is now 208 milliseconds
07:44:09.537: adding 23 milliseconds of audio buffering, total audio buffering is now 232 milliseconds
07:44:09.537: adding 23 milliseconds of audio buffering, total audio buffering is now 255 milliseconds
07:44:09.563: adding 23 milliseconds of audio buffering, total audio buffering is now 278 milliseconds
07:44:09.591: adding 23 milliseconds of audio buffering, total audio buffering is now 301 milliseconds
07:44:09.614: adding 23 milliseconds of audio buffering, total audio buffering is now 325 milliseconds
07:44:09.641: adding 23 milliseconds of audio buffering, total audio buffering is now 348 milliseconds
07:44:09.668: adding 23 milliseconds of audio buffering, total audio buffering is now 371 milliseconds
07:44:09.695: adding 23 milliseconds of audio buffering, total audio buffering is now 394 milliseconds
07:44:09.723: adding 23 milliseconds of audio buffering, total audio buffering is now 417 milliseconds
07:44:09.723: adding 23 milliseconds of audio buffering, total audio buffering is now 441 milliseconds
07:44:09.749: adding 23 milliseconds of audio buffering, total audio buffering is now 464 milliseconds
07:44:09.774: adding 23 milliseconds of audio buffering, total audio buffering is now 487 milliseconds
07:44:09.801: adding 23 milliseconds of audio buffering, total audio buffering is now 510 milliseconds
07:44:09.829: adding 23 milliseconds of audio buffering, total audio buffering is now 534 milliseconds
07:44:09.855: adding 23 milliseconds of audio buffering, total audio buffering is now 557 milliseconds
07:44:09.883: adding 23 milliseconds of audio buffering, total audio buffering is now 580 milliseconds
07:44:09.883: adding 23 milliseconds of audio buffering, total audio buffering is now 603 milliseconds
07:44:09.910: adding 23 milliseconds of audio buffering, total audio buffering is now 626 milliseconds
07:44:09.937: adding 23 milliseconds of audio buffering, total audio buffering is now 650 milliseconds
07:44:09.964: adding 23 milliseconds of audio buffering, total audio buffering is now 673 milliseconds
07:44:09.991: adding 23 milliseconds of audio buffering, total audio buffering is now 696 milliseconds
07:44:10.018: adding 23 milliseconds of audio buffering, total audio buffering is now 719 milliseconds
07:44:10.044: adding 23 milliseconds of audio buffering, total audio buffering is now 743 milliseconds
07:44:10.069: adding 23 milliseconds of audio buffering, total audio buffering is now 766 milliseconds
07:44:10.334: Last log entry repeated for 11 more lines
07:44:10.334: Max audio buffering reached!
07:44:10.334: adding 23 milliseconds of audio buffering, total audio buffering is now 1044 milliseconds
-----------
I also didn't voluntarily choose mac to work from. I had no choice due to my school course.
