20:09:03.127: Video stopped, number of skipped frames due to encoding lag: 1756/33246 (5.3%)
You do have some encoding lag going on.
In your logfile I noticed you have Windows GameDVR enabled. This may be a cause of the performance issue as even when you are not using it, just having it enabled in Windows settings it will always hook into the game process and commit resources (Similar to what OBS does when OBS is open, though more aggressively as it also buffers for replay recording)
https://www.howtogeek.com/273180/how-to-disable-windows-10s-game-dvr-and-game-bar/
While you are using a capture card which does take most of the rendering load off your system, your PC still does the encoding load.
You should have your Elgato HD60 source set to the default settings (In OBS source properties) and downscale using OBS Video Settings for optimal compatibility.
If you are only intending to stream, you would be better off changing your video settings to a canvas resolution of 1280x720, keeping 60fps. If you also intend to record game play you should downscale the resolution output via: Output --> Streaming Tab --> Rescale output setting: Box checked, 1280x720.
The good thing is you don't have any bandwidth issues in your logfile, you could increase your bitrate towards the optimal bitrate for 720p60fps, which is 5600.
Your colour format setting of 601 is also out-dated as 601bt YUV colour space is for resolutions below 720p (Or SD resolutions) 709bt colour space and partial colour format is optimal and default for OBS (Though you should be able to stream using any as Twitch/YouTube transcodes your stream on their end before it goes live)
Your bitrate is very low for streaming at 1080p60fps, you should be looking towards using 9k bitrate as a minimum or so for 1080p60fps (13k is optimal, based upon bpp calculation)
Simply put, you have a very low Bit Per Pixel value, 0.036bpp.
For very static background/slow motion games you may get away with a bpp value of 0.5 or so.
For high motion games you want to be as close as possible towards 0.1bpp (Going above 0.1 will provide an increase in quality output, though may not be worth the extra workload on your PC)
To calculate bpp value, the below formula is used:
(
Bitrate x
1000) / (
Pixel Width x
Pixel Height x
fps)= bpp
bpp formula source from the below link:
https://www.reddit.com/r/Twitch/comments/2dz7ru/bitrates_resolutions_and_quality/
Can you do another stream attempt for a few minutes' duration (Doing what you would normally do in-game) then stop the stream attempt then exit out of OBS, restart OBS then upload the 'last' logfile please. It will give a profiler statistics output of the stream attempt, along with an idea of potential memory leaks from browser sources, etc.
