How to modify vanilla mob properties

I'm new to modding and I'd like to change some properties of vanilla mobs (Attributes and AI, mostly) Using the MCreator engine; if it's even possible.
I know that functions and tags can be used to work around any potential issues, but if that's the case then i might as well re-create each mob myself.

I also want to know if it's possible to make a tool that only damages 1 type of mob.