Im running 25’s. I got PLENTY of room. Probably could run 32’s comfortably, but i have no desire to find out as its a road bike.
Having ridden back to back Conti 5000 28 and 32 on similar spec wheels, i'd say, don't dismiss 32C. Peak Torque has tested that assuming your rims are extra wide (32mm, presumably), there's no aero penalty, and no rolling resistance penalty to running 32.
The difference in comfort is so stark that i'm looking for a road bike that can comfortably run 32C.
How's the bike been holding up? I like the design, Trek is one of the rare brands that's not making "everybody else's frame".