Gerin: How would a single-class paladin work in nwn1? I have read here that it's good to get cleric levels after 4 of paladin, but what i f I just go pally all the way? Thx
Pure Paladin will work just fine, especially in NWN 1 where he actually gets his bonded mount.
Don't know who is recommending multi-classing Cleric; it's generally it's a bad idea to multi-class with a spellcaster class unless there's a specific ability you want. If you want cleric spellcasting, just play a pure cleric. If you want to play a holy knight, just stick with a pure Paladin and
maybe go for the Champion of Torm prestige class.
As for suitability to the campaigns, Paladin will work great in all of them.
On reflection, the suggestion for Cleric/Paladin is probably a suggestion for epic play, where you
begin above level 20. Your cleric spellcasting abilities would actually start to catch up to where they should be, and those four levels of Paladin would give you a noticeable improvement to your combat abilities. However, be aware that this character isn't going to mature until he reaches level 21. Only Hordes of the Underdark goes on long enough for you to reach such a level, and even then you'll be halfway through the campaign when you actually get there.