I bought a license for Mixcraft 9 RS a couple years ago and I composed all the music in that. (It's not the latest version of Mixcraft but it's good enough for me)
Composition-wise I mostly stuck to a single key per track (and a lot of the tracks are in C Major to be more upbeat) with a repeating, constant 4-bar bassline riff through the entire song, but with as much stuff going on as possible in those 4 bars to make it less monotonous. (Surgical Gardening or My City Is Sinking More Than Expected is probably the best example of this strat). I kinda feel like I fell into a trap of building every song the same way though, the first segment is always just the drums + bass and a lot of songs end with me removing everything except the drums so it'd be easier to make the song loop...
I'm reusing some instruments in a lot of tracks to add cohesion through the soundtrack (almost everything uses the same bass and drum kit VSTs for instance). I think I could've gone further here and actually settled on some sort of "musical identity"... everything is kinda just random stuff with the only thing in common being that they should make you wanna move fast, and I didn't put much more thought into it than that.
I generally composed the music before I made the stages and worked very fast due to the jam time limit (making like 3 songs per day), there's a bunch of discarded songs that were too bad to use as a result (and even with the stuff that made the cut, I'm a bit unhappy with the quality - the song that plays for like 10 seconds at the start of the cruise ship mission for instance). Maybe having a main theme and making every cutscene song a remix of that would've helped here...