Fwiw on my 29er the giant s-xc2 rims internally are 19mm, and I run 2.2"(56cm) tires. I've found pressure to be more important then tire size. I'll inflate my xkings to near max pressure of 65psi and hammer around on pavement. It rolls well but it's noisy.

So to the OP, get the widest tire in your preferred tread that's economical and well stocked. You can always bump up pressures for a quicker ride on wide tires. Get one with a sticky compound and be done.