So is it just reset to a base default once you switch classes? or will it "roll" for bonus points and distribute them randomly too? If not then, man, why would you ever switch classes instead of just rolling for a 40-50 and dump points until you get the class you want right off the bat?
the main reason to reroll classes is to build up your HP super high while maintaining the leveling momentum (though HP gains are diminishing from repeated multiclassing I think), and spells learned/spell slots carry over to your new class.
However, some pre-made characters, including the MC, start with unique skills that they shouldn't have in their given class. For example MC always starts with Counter, a very valuable skill that lets him counter-attack enemies that attack him if in range.
These skills are lost if you change jobs and you won't get them back if you change back. This means you should plan carefully from the get-go for the MC so you don't waste an otherwise extremely valuable skill that only a few classes learn later at a higher level. MC also gets spell slots naturally so I'd shy away from caster heavy characters and stick to hybrids like Druid, Lord, Assassin, or Spellblade.
Another tip: Some pre-made characters are absolutely BROKEN. In Northrop there's a Sylph at the guild with Elemental, Alchemy, and Holy spell slots, and 9 spell slots for every spell level up to level 4, with 4 spell slots for each at 5th level magic, and she starts as an Assassin. Insane.
When starting out, it's tempting to make your own heroine at the start but I'd consider looking at the girls in the Guild before making your choice; Elf has really good spell slots for a level 1 party member, making her a solid option for multiclassing a few levels in so she doesn't clash with Liselle, who is with you throughout all of Act 1, and there's also a Human Fighter that starts with Protect, which is a crazy good tank skill normally exclusive to Lords.
RECOMMENDED FOR THOSE WHO WANT NTR BATTLE/INN H EVENTS FOR HEROINES:
Invest in Monk. The reason for this is Monks are unique in that they get higher AC with the less weight they have on them. If the Weight encumbrance number is highlighted in Blue, it means they're barely carrying anything at all, and it gives them a massive boost in Defense.
So how do you capitalize this and how does it relate to everything else? Simple:
DRESS THEM LIKE SLUTS! Make them wear little to no clothing, make them run around naked if you must to capitalize on this, and watch as her Excitement level exponentially increases, along with male party members's Lust. In terms of battle-rape, enemies will prioritize her if she's barely wearing anything, cuz it's easier to fuck her in that state, so they're likely to capture her more. The lust build up will also help them get fucked by your male party members during Inn segments, so keep at it by dressing them in as little as possible.