I played NWN2 with a dwarf fighter8/frenzy berserker5/weapon master7.
My first NWN2 playthrough was with a Drow Bard 20. Never so much as touched a weapon after the intro, all buffs and debuffs afterwards.
Do these classes exist in NWN2 and is this effective to?
Yes, all the classes from NWN1 exist in NWN2, although in some cases the rules have changed.
The most important thing to note is that the improved critical feat
does not stack with the keen weapon property in NWN2, but it does in NWN1. This greatly reduces the craziness you can pull with the weapon master by stacking critical enhancing abilities, but it's still pretty strong.
I know that you can have only 3 classes in NWN1.
Yes, three classes in NWN1, four in NWN2.
Are there more or less chances for alignment shift in NWN1 than in NWN2?
Each campaign handles it differently. In general the shfits are significantly less prominent than in NWN2. The original campaign is actually the most reserved in the entire series for alignment shifts; it only hands out good/evil shifts, and only for unambiguous acts like refusing rewards or threatening to murder people.