Vintage guy and vintage bike. Have been riding the old Schwinn with 27” tires and 70-80 lbs for decades. Fancier vintage bikes now with nicer tires. 70-75 seemed nice in some pasela gravel king 32s on an83 Trek. I weigh 165lbs. Newest vintage bike is a wider rimmed tourer that I put panaracer pasela 35s on. I started at about 70 psi. Last ride was with 60 in front and 65 rear. Smooth quite riding tires it seemed. I ride”soft” so wasn’t concerned about pinch flats. Do others go less? Maybe just try and see I guess. I would think at a certain point I would be giving up speed.