This is a recreation of an old Fallout mod that was never finished. Fight feral ghouls or help the desert rangers in their constant fight against raiders. Be an angel or a devil in the flesh. Everything is up to you.
Anon gave a very good remark so to address it - yes muni will be caps.
As for horses not being around in canon,All Roads, the comic Chris Avellone worked on that is set just before New Vegas, shows that at least one NCR Soldier had a horse before the Bitter Springs Massacre, FO1 had either a mule, so hybrid horse and donkey, or straight up donkey depending on localization, though Avellone has stated the All Roads horse was a mistake no one noticed until it was too late, so take that as you will. As for cats, while you don't actually see them, Fallout 2 had one of the Broken Hills residents mention his pet cat, and one of the Den Residents mention she had a cat as a child, until it was killed for food, BoS has you find a prostitutes cat, turns out its dead but it was still around until recently, and Van Buren had plans for a number of both domesticated, wild, and North American Big Cats to show up, so no, cats are not a Bethesda Neologism in the Fallout universe.
Anyways as to the mod stuff, this is looking good, and I wish you luck with your work, and hope this project actually comes to fruition and doesn't die out like all the previous Fallout for M&B mods did. Also if you choose to include any kind of mounted unit and you don't want to use horses or donkeys or the like, I would suggest looking into some of the OSP packs that have motorcycles or small cars, since there are a few operational vehicles in some of the Fallout Games.
Animal mounts work well when 50% of your factions are tribals.
As for vehicles - they never got them right sadly.
Unless there is a way to make unique motorcylce sounds without replacing the horse ones motorized units wont be used.
As far as I know, you have either a motor sound, or the horse sounds. Not a modder myself, but just off the other mods I've played, it's always been either or. Not sure if it's an engine limitation or not. And yeah, tribals with critters are always fun, so that's something to look forward to.
I actually got some time to make a "research" on he topic of horses. Looks like horses still exist in Fallout universe as they are referenced by a number of characters if the info here is correct:
Fallout.fandom.com
you could make the mounts brahmin? I don't know or not include them tbh unless merchants or something
Yup we will try to add brahmins. There is an idea to make brahmins and dogs roam the streets in some settlements (not static models but actual NPCs). They will not attack you though, for obvious reasons.
Mod looks cool though
Cheers, mate.