My trailer doesn't carry the burden of showing a good clearcoat. Before I'd try anything aggressive on a good clearcoat, I'd test it in an inconspicuous location like behind the roof air conditioner. A product like Goof Off removes dried paint, so it just might remove something like clearcoat . . . just saying.
I use it to get the label off peanut butter jars.
My trailer didn't carry any bumper stickers. I once got some pinstriping remover from an auto body shop supply store to remove pinstriping without removing the paint on the car. That worked beautifully to remove pinstriping.