Just got both BG1 and 2 EE in the sale. Before I start playing I was wondering if anyone could tell me the essential mods to get for both, if indeed there are any.
Also Is it possible to do all the companion side quests in one play through, or am I best to stick to a set few?
Finally can i import my BG EE character in to BG2 EE?
In BG1 most of the companion subquests are very simple. Only the companions introduced in EE have more elaborated quests, though in my opinion these are of questionable quality.
In BG2 all companions have rather long and interesting subquests. While theoretically possible, I don't see how you could finish them all in the first playthrough unless you are using guides and you are willing to sink really really long time into the game. The issue is that often in order to move the plot further some time has to pass in game and some of the quests (expecially romance) are quite long. So you will end up waiting for a dialogue to trigger.
In BG1 my favorite companion for the good party are Imoen, Kivan, Coran, Minsc, Dynaheir and one additional character depending on the class of my main character. For the evil party we have Edwin (the best spell-caster in the game) and Kagain (dwarf-warrior). I still usually try not to go pure evil so I can have neutral characters in my party.
In BG2 my favorites are Edwin, Minsc, Jaheira or Viconia (for good and bad party respectively), Keldorn or Korgan (again, good vs evil).
But you should try for yourself and see which characters you find most useful. I personally, never care to have the additional new companions in my party as they really annoy me. Similarly, some will say that Aerie in BG2, who is cleric-mage is an awesome character to have in your party, but again she annoys me so I rarely take her with me.