Looks like you're overloading your CPU -- majority of missing frames are from encoding lag. You're asking your ryzen 3 2300x to do 720p60 fast encoding, which is barely within its capability. Anything you do that puts a temporary CPU strain on your system will probably result in the encoding lag you're experiencing.
What you could try is using the AMF encoder on your RX570... unfortunately I don't know enough about the AMD GPU side of things to be of real help there with recommended settings.
If you do want to keep using x264 encoding, I would definitely recommend doing everything you can to streamline your computer's performance -- kill any unnecessary background processes, make sure OBS priority is set to High. Also, make sure your media sources are unloaded when not in use -- 1080p.MOV is set to be always loaded, and not use HW decoding, so that means this is a constant load on your CPU.