Composition sounds cool! not much to say about it lol as I don't think I have much to add there...
Regarding what you said about the mixing -
I'd try to fade the instruments where I don't want these clashes.
I saw you used MuseScore and I have no idea how it works (More of a sheet music reading rather than a DAW right?)
but I did find this comment from the forums:
"For playback of a fadeout, you can use a decrescendo. See:
https://musescore.org/en/handbook/3/hairpins#cresc-dim-lines
If it's a musical phrase (e.g., a few bars) that repeats during the fade out, you notate all the repeated bars.
Have a listen to this example:
4 Bar Fade Out.mscz
Also, see:
https://musescore.org/en/handbook/3/dynamics
Especially:
https://musescore.org/en/handbook/3/dynamics#adjust-properties
to edit the velocity (volume) of a dynamic.
You can fine tune the velocity of note(s) in the Inspector:
https://musescore.org/en/handbook/3/inspector#note"
Hope that helps!