when i use this mod, horses disappear!

This could be an issue of conflicting mods. All the files are correct after checking and horses appear in my game as well as my co-authors. Check to see what other mods you have that might alter the horse meshes.

a second capua exists to the left of the Arevaci :o

Screenshot please?

carthage is the same with its starting territories

The Etruscan League's culture is Italian (Roman), but all the bonuses to cultural conversion that they get are conversion to Latin; religious buildings, the Romanisation edict, and their faction bonus.
I don't know if this is intended or not, but it looks like a bug.

The Etruscan Citizen Hoplites and Etruscan Hoplites are basically the same unit, but the EH cost 100 more and upkeep is 60 more.

The Diplomat for Piscenum, Umbria, and Roman Repulic are bugged to use the last selected factions diplomat head (i.e. if I click Carthage or Boii, then I click one of the listed, the game uses the one I last chose).

That's a set of bugs it seem possibly from CA since the ETL were never meant to be playable (although the faction bonus is due to us reusing the one of the Roman houses traits)

Treat it as a bit of variety :D Do they have the same abilities? We could change that to give them a slightly altered battlefield role

Ah, that's an interesting one, but I'm not sure what might cause that. Thanks for the bug-hunting :)

When I start game as carthage,there is a full stack Roman Army with expensive troops present in one of my island provinces (the one above the carthage).

Whenever I personally command a battle and fight alongside alongside Capua (not for autoresolve) the game crashes.

Crashing on all battle loading screens. Ony mod installed.