>>324238354
Easiest is bigscreen VR and mpv or whatever regular player you use (bigscreen just mirrors your desktop). Has nice dynamic lighting of their environments.

Second easiest is an overlay like desktopplus or XSOverlay in the game of your choice, vrchat for the most map variety. No interaction between the video and the environment though.

Medium hard mode is vrchat video players, which you can get the nice dynamic lighting, but you have to transcode the video to bake in subs, and host it over http to get it to load (localhost is fine, or Dropbox if you're not smart enough for that).