I've just started playing and I can already tell you that there are five types of weapon mods (so far) and four types of armor mods. The five types of weapon mods (so far) are sights, magazines, and barrels for guns, as well as grips and attack mods for melee weapons. The four types of armor mods (which can only be applied to armor, not headgear) are armoring, gadgets, skill kits, and utilities. I haven't even left the first area yet, at least try to post with some details.

Can you recover a broken down weapon? How so?