Try changing x264 preset, like maybe super fast.
Set output / scaled resolution to 854x480 or 1280x720, both is good for YouTube without extra scaling by YouTube itself.
There is an option to use custom ffmpeg output that allows a choice of more encoders like huffyuv which may use less CPU, but need a lot more disk space. Advanced, output colorspace may need to be set to i420 or RGB depending on encoders.