A gravel bike is the construct foisted upon us after selling us a mountain bike and then endurance bikes.
On a road bike, 28 or 32mm are plenty for most gravel where I live. For tougher stones, I ride my road bike with 650b x 38mm compass extra legere tires. If anything is technical, it is Mtb although I do wonder what I would race on the Tour Divide had I not had my injuries.
I use backpacking bags although recently bought a Tailfin setup
I use two rear blinkies.
I carry two front battery powered lights (one backup).
But gravel for me is more incidental rather than a destination. Some of my routes have gravel, most don't. 25mm isn't fun. 32mm is fine. for me. YMMV