Ah yes, well, a cover is a great way to protect the finish of the RV; some recommend super-snug fit with zero movement, while we have a relatively light flow and less than super-snug on ours. We have the Classic Accessories Over Drive PolyPRO3 Deluxe Travel Trailer Cover or Toy Hauler Cover, Fits 35' - 38' RVs (80-356-213101-RT) found on Amazon currently at $269. We had one from another maker 4 years ago (2016 29BHS) that actually ripped in half during a windstorm...replaced under warranty
We also wash and wax, but I think the UV rays will take their toll on any painted or wrapped surface. We also cover our truck, and got top dollar in trade-in on our last one (2014 F-250); the paint still looked beautiful, no scratching from the cover. To be fair, we did pay for the upgraded cover with the brushed interior lining. Though sold as "waterproof", that is <not> how it works out if you're hoping for a fully waterproof one...that would be more of a "tarp", which is NOT a recommended covering in most cases.
As far as your trailer goes, your experience may vary depending on how methodical you are on cleaning, covering, tightening, monitoring, replacing as needed. Our 2019 Outback still looks great