YouTube resolution smaller than output resolution

[AkeMake]

I am quite a noob with OBS. I have tried to google what settings I should put down to my OBS but for some reason, it hasn't worked for me.

I am live streaming our meetings to YouTube and my main problem is that no matter what output resolution I choose in OBS my YouTube videos are only 360p resolution. Also, YouTube constantly warns about buffering because it's not getting enough video. I am only live-streaming and not recording. My hardware solution is also a bit strange but I don't think it should affect the resolution.

I am using a Macbook Pro with
processor: 2.6 GHz 6-Core Intel Core i7
memory: 16 GB 2667 MHz DDR4
I have two cameras: one is a 1080p webcam connected straight to the computer and another is a 4K GoPro connected through ATEM Mini Pro. Both cameras are so far from the target and they don't have zoom on their own so I have manually "zoomed" them a little bit in OBS by dragging the video source bigger than the window size. Of course, this way I lose some video quality but I should still easily get decent 720p from my webcam.

My streaming encoder settings are
Rate Control: CBR
Bitrate: 7000 Kbps
Keyframe interval: 2s
CPU Usage Preset: veryfast

Base resolution: 1920x1080
Output resolution: 1920x1080
Common FPS values: 30

My internet speed should not be a problem. Speed test using Wi-Fi gives an update speed of 18 Mbps. For some reason, my encoder is struggling with live streaming because it constantly says that encoding is overloaded. OBS is constantly using about 30% of my CPU. I cannot figure out why my YouTube video is only 360p and not 1080p or even 720p.

 

[AkeMake]

I had a lot of tabs open in my Chrome. I closed almost all of them and that way I was able to release some CPU. Now OBS uses a somewhat constant 40% of computer's CPU fluctuating between 20-50%. OBS is still saying encoding is overloaded. My CleanMyMac software tells me that the computer's CPU load is more than 90% even though I don't have other heavy programs running except OBS. Google Chrome with 4 tabs open is the second heaviest CPU-using program after OBS. Heavy CPU usage must have something to do with my bad settings in OBS.