How does OBS work with FFmpeg to encode recordings? Why does OBS only list a sub? Is there a way to use any supported FFmpeg encoder on OBS?

[YousufSSyed]

OBS lists only a subset of encoders supported by FFmpeg in Output > Recording > Custom Output (FFmpeg). Ultimately, I'd like my recordings to be encoded with x265 on my MBP, would that be possible? Either way, how could I specify what encoder to use in FFmpeg that's not in the dropdown of encoders in said menu?