I think you are going kinda big on the tire size, but the best answer to you is a bike that takes fat 650b tires or fast lean 700c tires.
For fast road rides (averaging 20-30, with higher peaks) I use some light wheels and 700x28mm tires. My bike is as any road bike set up like this.
For gravel I’ll use 40mm tires. Really, that is as big as I need to go for this bike, for gravel and light single track – the kind where I don’t need a suspension (not tons of rough rocks, roots, or jumps).
It is fun to put some 54mm tires on the bike and go play. But at that point it really feels like a drop bar mountain bike. I would be better off just riding my mountain bike in those conditions. The fat tires slow down the handling slow down acceleration, and my top speed. Even though the “rolling resistance” is great, the acceleration and handling is (obviously) much different than with the 28’s (or the 40’s).
But, I find “under biking” to be rather fun – going a little outside of the bike’s comfort zone where I have to read the trail and pick my line…