Are there toll roads? And is it better to go to the visitors center or the overlook?

No toll roads only in state parks

There are entry fees for getting onto the "loop". You can do both the overlook (public rest/viewing area off the public road), as well as the visitor center on the loop. I think you pay the fee (or "toll" if you like) at a booth before the center. The overlook is a far away vista view, where the loop takes you into the area with many stopping areas (that are trailheads for hiking paths, some popular climbing areas, and a few indian historical sites. My opinion is that if you're going to bother driving out there, do the loop. Guided tours can give lots of added information to make it more interesting.

And no drive around and get out to walk the trails