Glad you're enjoying it!
To answer your questions:
- the variant types only differ very slightly from the main class; they have fractionally higher stats. Each class has two variants; rare and very rare - the rare gets 1-2 extra stat points, the very rare 2-3 extra points. The difference is generally not noticeable other than at very low levels.
- how do clerics/bards recharge mana? With difficulty. Basically, there are 2 ways:
- some loot/treasure gives mana points
- at the start of their turn, if they need mana, and they have some xp 'spare' some of the xp gets turned into a mana point. (This makes them slower to level). The best way to earn xp is to fight monsters - but that's not easy for a cleric/bard.
- (coming soon, there will be a third way - stores that stock mana potions)
(Best strategy for Cleric/Bard; hang back, use mana sparingly, hoover up loot. They're the hardest class to do a solo run with. I have completed a couple, but it's tough)