Many different methods depending on substrate and how hard they are to remove.
If the unit is fiberglass, and white, it is easy to burn/discolor with an eraser wheel. I keep the eraser wheel to a minimum on gelcoat, especially white.
Know that you’ll have ghost stripes after removing that will either require a cut n polish or may not totally disappear even with that level of effort. On the flip side if you’re having the same graphics remade it’s easy to see where to install them!
The quickest and easiest method is a heat gun and a razor scraper. Know that when they’re fresh or sharp they dig and gouge easier. Actually one application that I prefer a more dull blade for. Gentle heat and scrape. If a piece will peel by hand, peel it.
Clean up residue with most any common solvent. Goo gone, Adhesive remover, prep sol, lacquer thinner, gasoline. I wouldn’t use any hotter solvents than those.
It’s a chore and I estimate it would take me a half day at least jsut to get all the decals off of the truck camper.
If I had the time, I’d remove the decals. Mine are peeling but I keep trimming them up. Works since it’s like a “mud splash “ pattern.
Then I’d vinyl wrap it either in its entirety or selectively. Rv type structures are pretty easy to wrap because mostly flat surfaces.