I used OBS in an upcoming gameplay video (first ever actually). It works fine, but somehow it does not like to work with my samson sound deck software. So I record my audio from my microphone elsewhere. I record in 1080p30 as my rig tends to dip below 60fps at times, and that messes up the video something fierce. OBS can record at 1080 no prob!
You do need horsepower. You are asking the PC to game and record at the same time. I also record to an usb3 external drive so I don't clog up my main HDD with writing tasks.