Pets can level up! Each time you make 5 RP posts with them, they gain a level (each post requiring at least 5 sentences). However, it's not super necessary to level them up unless you're planning on joining the war or participating in (very) occasional tournaments. xD It's a little tedious but it's also kinda fun? You have to update the stats yourself, all of which can be found in the Pet Stats section. Also each RP area gives different buffs to certain stats, but the default is +1 to all stats per level.
Also, hello!
And yeah pretty much!! "Pets" is kind of a funny word; it's more like a database for all your characters that other people can view! So "actors" does make a lot of sense. ovo