Short stops along the way - allowed where?

I've been reading a lot about where you can and can't park overnight. Tons of info out there about that. But what about when you're on the road and want to stop to see a small attraction before getting on the road again?

We used to do that all the time when road tripping through the US with a car. We'd plan our day so that we'd be driving for 3 hours, stopping at some town to stroll around or maybe see a small museum, then drive for another two hours and do the same and finally drive for an additional couple of hours to our final destination for the night.

Now, with a car, you can park just about anywhere. Sure, sometimes we'd have to find a parking lot (paid) or metered parking in a big city. Other times, in small towns, it's often a matter of just pulling by the side of the road and park behind another vehicle standing there (as long as there are no signs telling you not to). Parking in a residential street was never an issue if we wanted to see people.

Looking at videos of some of those large RV's people drive around in makes me wonder. What do you do when you just want to stop for 1-2 hours and leave your rig while sightseeing? Do you always look for a Walmart/Costco etc? I don't recall seeing too many RV's or commercial trucks in the parking lots of shopping center. Pretty sure you can't just park in a residential street, right?

Or do you just plan ahead so that you move the big RV only from one campground to another and then do your sightseeing around with the tow vehicle or toad?