Two Questions.

[Megas Methuselah]

1. Yes: Imperator, Africanvs, Asiaticvs, etc. all replace your character's surname(s). Furthermore, Africanvs and so forth would not only be used by your victorious character, but would also pass on to his natural sons.

EDIT: It's pretty damn well cool how sons can inherit the names. Thx, EB team!