If I have a day or two to visit Yellowstone..,.

You can drive thru and see a lot of the features. In a car. But many of the parking areas to see those features are small and tight. Some have RV parking. Some don’t. Likely as not the RV spaces will be occupied by cars. But that time of year they will all be crowded and very difficult for a large RV.

I would try West Yellowstone for 2-3 nights and drive the toad to sightsee.