So I have the collector's/special editions of both games, but testing X-Wing just now it picks OPL3 FM synth music. How do I enable CD tracks, if there are any? I am aware of the "better midi" thread, gonna look at that later.

Or is it just the third game that has cd audio music?

Regarding midi, is this soundfont available (tie fighter)? The video description is vague.
https://www.youtube.com/watch?v=zuwMv2xzPiM

I'm also aware that the games use the iMuse system, so I'm gonna play with midi but was still curious about any cd tracks.

The DOS versions only had MIDI music, the windows versions had CD audio music that only had three tracks instead of the adaptive MIDI iMuse system.
You can get much higher quality MIDI playback with VirtualMIDISynth and a good soundfont (I usse Timbres of Heaven, TIE Fighter in particular gains a lot being made with high tier MIDI devices in mind) after tinkering a bit with the options of DOSbox and the game installation (mostly to make sure the in-game music is set to GeneralMIDI).
This is to give an idea of what the DOS music sounds once set correctly using the above:
X-wing
https://youtu.be/csKOVt2FfRc
TIE Fighter
https://youtu.be/qRyATbCrAJk

The CD versions for DOS had a lot of digital audio which ended up being heavily compressed in the windows versions to make space for CD audio music.

You mean the 1998 release? I checked the 1995 cd-rom version of tie fighter off archive.org and it didn't have redbook tracks, checking x-wing cd-rom now.

Neither had redbook audio before the windows remakes.

Yeah that checks out.