As for the question about freewheel or freehub,
A front freewheel set up uses a fixed hub with a fixed sprocket on the back and a freewheel on your cranks
A freehub has the ratchet system like the freewheel at the back, so you use a fixed sprocket on your cranks
If you're gonna upgrade your cranks, get some ISIS ones, isis is so much better than square taper in so many ways
Snail cams:
If your dropouts have got a threaded hole in them you can put the snail cam bolt it, you can use snail cams. Loads of frames come with the holes in them, Not sure on onza frames but I imagine they have them too