Hello o/

I would like to be able to configure the output of the Auto Compressor, so I can modify which mod the output comes from, in cases like 9 Ingots -> Block. A config to switch prefered mod for outputs would be fantastic, but I don't know how hard that would be to implement.

You should be able to use a mod like CraftTweaker to remove the unwanted recipes. Ex Compressum loads its Auto Compressor registry after CraftTweaker has run, so it will only take the remaining recipes into account then.

Is the Auto Compressor registry just built on all recipes that fill 2x2 or 3x3 with one ingredient?

Yes, but probably it prioritizes them differently than Vanilla does, which is why you get a discrepancy (e.g. Vanilla Crafting Table crafting compressed blocks from Mod X, while Auto Compressors craft compressed blocks from Mod Y). The best solution to keep consistency across all places is to only have recipes that are meant to be used left enabled. Hopefully in a future Forge version there'll be better compatibility for these kind of material blocks so not every mod has to provide their own block versions.

Alright, thank you. Fingers crossed for a neat solution from Forge 1.13 :D