I have noticed that the ultra fast belt has the same speed as the superior belts from Krastorio 2, but the former are much cheaper and can be obtained way earlier on than the latter
My proposal is a setting that when enabled, removes the ultra fast belt, and changes the extreme fast belt recipe to take superior belts.
Potentially also could make the belts from the mod require advanced tech cards to research, although this doesn't really matter.

Ran into the same "probleme" has you.
and made a mod for this type of situation:
https://mods.factorio.com/mod/UltimateBelts-K2
(good of old shameless self-promotion)