If I compare 12 stack inserters with 2 miniloaders (both options can fill 2 blue belts) unloading a cargo wagon, which way is better regarding UPS?

This mod needs definitive more UPS than ident mods. We have testet all 4 mods for the loaders and this was 3 times more bad for the ups.

But i can talk many. Try it on yourself. install all 4 and test it with 10.000 loader each and show what debug say.

While this may be less efficient than other mods. This mod should almost certainly be more efficient than regular stack inserters, since under the hood each miniloader is essentially 2 (very fast) inserters. So for this particular scenario you're going from 12 inserters to 4.

Normal loaders is better than miniloaders now, miniloaders should only be used if you need fancy circuit stuff