I've ridden moderate gravel with 30 and 32 mm tires like GP5000 but the side walls take a beating unless the stones are smallish. It sounds like your surfaces are modest and that GP5000 would be ok on the paths/levee and would excel on pavement. That is probably what I would ride, if I understand your surfaces.
Pretty much all the tires recommended would work well on the "gravel" but some would be better on pavement. If most of the riding is on paved roads and the ride is long, do you want to purpose made gravel tires?
On rougher gravel roads, I tend to like the Herse/Compass tires in terms of comfort and speed. However, the casings in extra legere are fragile. The 700 x 35, 650B x38 or 42 are slower than the GP5000 on roads but clearly faster and more importantly would have better control on gravel.