The Toughroad is 700 x 42. Frame shouldn't be an issue unless you plan to haul tons of gear and get big air off of drops.
You may want a suspension fork but it isn't a deal breaker if you want a touring bike that is capable of some moderate off road riding. If you want to do really hard off road you probably want a full suspension bike anyways. no touring capable bike is also going to be great at technical mtb.
FWIW, I mtb with a couple of different bikes. A rigid 26" I put a cheap suspension fork on (also tour with that frame).
A rigid fatbike (also tour with that frame).
And a rigid 26" single speed.
