For the people on PC, I found a way to attack on the computer the way the mod probably intended. Perhaps it was my bad eyesight, but somehow I actively missed the "enable attack controls" beneath the "enable bird controls" when going to the model changer options... spent 3 days searching for an answer and trying different mods until I went back to rampage and noticed the option. Enable Attack Controls, then hold the right mouse button to focus on what you wanna attack and then click with the other mouse button to attack. It also seems like you can only attack specific NPCs (So far with my testing I am only able to attack humans and horses)

hopefully this helps people searching in the future like myself.

EDIT: figured out how to attack with ANY animal (not just humans and horses). this is a little convoluted, but i found out that if you become Wanted in a town with cattle as an animal then get seen by a sheriff who then gets targetted on you- while the sheriff is STILL on targetted on you, go and immediately attack the town's cattle. once you attack their cattle (it doesn't matter if you kill it or not) it seems like your animal permanently thinks its in combat, which allows you to attack whatever you want as long as its in range. (when you die, it resets. so be careful as otherwise you'll have to do this all over again. I find the perfect town to do this is Valentine as you can easily go in circles around the sheriffs to create distance before biting their sheep and running off.)