Either you can see it by just looking at the file names (example: "Starfield -
WwiseSounds01.ba2"), or by using HxD and search for wem specific texts, like this
And now, how about to know if you can compress them with msc/xtool:mflac..
Just test it lol
In this case for Starfield, you cannot use msc or xtool:mflac, because the wem files are encoded with ogg vorbis.