First off is it wise to complete the first chapter with just your main character? I heard you gain more levels by doing this than having help from the others. Second off for the first time through Im thinking of downloading some mods and trying to get an all evil party put together. How wise is this and are there any benefits to having a whole party dedicated to one alignment?

It is called soloing - whole game can be beaten playing with one character. If you have less or no party members, earned exp. points are divided on less characters. So, if you are alone, you'll get all of those.

If you have NPCs of very different alignments, they will argue and sometimes even fight to death. If you act purely evil, good NPCs will eventually leave (and vice-versa). If whole party is created by yourself, alignment is not a problem.

If you don't want the caracters you'll meet you can do it. If it's your first time however I think you should use a party,so you can get the basics and use startegies. The first game a party is best , not ony for the basics but the NPC interactions are very cool. If you solo your first game there isn't a new challenge.

For the mods I think you should play the game first the way the developers meant the game to be played. The game is great and mods are just for a new experience.

Having an one alignment (or as less as possible) party is handy cause NPCs won't leave for the reputation if you keep it as low/high as it should be for your alignment. The NPC interactions between different allignments are cool though. You'll always have different alignments since there aren't that many NPCs.