i'm curious about the various speeds you can play at? 1/2, normal, etc. what does each do and whatnot and which is the best one to be on while playing the game?

The game speed affects things like villager aging, nursing moms, how often the crops grow, villager food consumption and productivity - basically how fast everything progresses in the game. If you're not around to keep an eye on things, slower speeds are best. If you're actively playing it and want things to move along quickly, choose a faster speed.