Mac users can get a very nice front end to mpv with
https://iina.ioBonus trivia: Plex Media Player uses mpv as the video player
That is... not a glowing endorsement. I've had more bugs and player failures from Plex than any other media software I've ever used.
Streaming or player errors? Plex has basically never failed to play any video I've ever given it, but a bad connection can totally ruin streaming. I wish they would implement pause and allow to buffer.
In my experience Plex has a serious problem with determining whether or not it's capable of playing a file back directly without converting. I regularly have to switch it to "convert automatically" to make a file play.