Is there a way to disable or set the stacking to default 1 for all the inserters?
As soon as I researched belt stacking all the inserters switched to the max stacking, and I have around 3000 of them, I would hate to reduce the stacking of each one by hand. :D

this is regular factorio behaviour, researching stacks increases stack size on inserters. Its not something the mod changes.

And why would you want to change this anyway? unlocking inserter stack size from 1 to 2 doubles its speed, its something any player wants. Only a few selected and particular designs need a restraint on stack size, not the whole factory.

After doing a bit of research I found that the main restraint point are the k2 loaders which are also now stack-unloading, maybe I mistyped that in the first post, inserters are fine for the most part.

I would have to disagree with Kjorn's request. The benefit of default increasing stacking I feel like is an intended behavior and what I would prefer. There are much fewer scenarios where I'm decreasing the stack size. Also, love that the loaders are stack-unloading; I can't think of any scenario where I don't want that behavior, and again, stack size can be overridden for each loader if needed.