Just to put in my 2c regarding your question about whether you should recruit everyone or not:
You can have a maximum of six characters in your party and I would definitely recommend traveling with a full party whenever possible. The game was designed with a well-balanced player-controlled party of six characters in mind, so that will give you the best chance at beating its challenges. Well-balanced, in this case, means you should at least have the four main fantasy archetypes (Warrior, Healer, Wizard and Rogue) covered. Which, in AD&D/Baldur's Gate terms means that you should have a strong Fighter or Paladin, a Cleric or Druid, a Mage and a Thief. There are many recruitable NPC's available in BG (25 in total), so there are plenty of options in that regard and getting to know each one's personality and skills is one of the best parts of the game.
Remember also that you don't need "pure" classes to fulfill the needed roles -- a multiclassed Fighter/Cleric, for example, with a decent Wisdom score (let's say 16) will do fine as a healer. There are, of course, certain advantages to having pure classes in some roles, but it is by no means required. Just have fun with it and remember, if you only want to replace someone temporarily, to leave them in a place that is easy to find and get back to (for me that is often the Friendly Arm Inn) so you can pick them up again at a later stage.