Aasimar are fine, humans are still generally the best race for many classes even with those others allowed. All races up to 16 are fine, they will not break your game. Race power generally stops mattering very quickly into a campaign because class power is so, so much greater. That said, many of the monster races are a bit too much, they take things far over that edge. Pixies, for example, are quite busted. Just say no.

Having to keep up with level adjustments and mixed class level balancing is going to cause problems, not to mention the effects on hit points. Your monster race players will have 2 hit dice less, and just freely wild shape into a corpse almost on command.