Like, can they change shape if they were known for that in their legends, do they have to stay within X feet of their masters, how often do you have to feed them?
Shapeshifting is a Skill, yes, and this can also be used as a Noble Phantasm if you so wish. They do not have to stay within X feet of their Masters, and they do not need feeding, but ideally you probably should so you don't get killed by the gluttonous ones *cough*Saber*cough*.
I had assumed that Antihero meant the standard "Morally ambiguous Hero", under those standards I will probably put him under hero for now. He is probably at least looked up to in France, right?
The Nasuverse is weird like that. And most real-world figures could fall under Hero or Anti-Hero depending on their reputation, with only serial killers like Jack the Ripper possibly falling under Monster.