The tires pictured are 38 Gravelking SKs that measure 40mm on those Black Inc wheels. I raced that setup at Texas Chainring this weekend, and it was plenty of clearance. In a muddy race, I would use 32s and I think it would be fine for even Landrun style mud.

My previous bike was a 3T Exploro, and on it i very rarely raced or trained on anything wider than a true 40mm tire.