Historically, the series has featured a tiered upgrade system. You could level up to 20 in whatever class a unit was. But you could find a special item that could switch them to the upgraded version of their class, starting over at level 1 (but with much higher stats). You wanted to wait until 20 because stat growth from leveling was important. Later games added skills you could equip on characters, that impacted character performance in a variety of ways.
Combat was historically a rock (sword)-paper(spear)-scissors (axe) affair. With another triangle for magic, and bows > fliers. Advanced classes often granted the ability to use different types of weapons. When attacking, whatever weapon you used was your “type” for the next turn so once you got the ability to use multiple types of weapons you sometimes needed to think hard about switching and when. The game also featured a purely garbabe durability system for gear. This was mostly just tedious between battle bullshit.
This game is dispensing with all of that to some degree. Sounds like there are 3 or 4 tiers of classes where you start out very basic but start specializing as you go up, and you can apparently switch to previously used classes whenever you want (and there’s no need to worry about maximizing experience before switching).
The series then went sort of nuts with marriage, and children (and being able to “fuse” classes/skills in offspring), and such. There’s no dialog trees in the classic RPG sense or anything like that. It’s a fun series, though.