I ride wheels, 25 mm internal, on a different bike than you own so I can't say what might fit yours. What I can say is my tires say 28 mm on the packaging and measure out to 33.something on those wheels.
You want a few mm clearance on either side of the wheel, vs the frame. Even if you never ride gravel, there's crap in the road, sometimes wet crap, that can stick to your tires. Also, you said you're a Clydesdale; the wheels might flex a little under you during hard efforts like standing to climb, and it'll be wobbly if you break a spoke.