No experience with Model Y but I bought an outdoor cover (probably similar; maybe made by same company?) for my Model X and am very pleased. It is light gray with white liner. (Probably artificial fabrics.) That soft inner liner seems to protect the paint. Fits snugly over side mirrors (I have them fold inward to make that easier.) Seems very well designed and built--characteristic Tesla accessory quality. NO cover is totally easy to install and remove, but this one goes on and comes off well. And with experience it is easier to do (just have to learn to orient front and rear). It has an elasticized bottom edge. Plus you can lock it underneath the car with a cable (not included), if necessary. I have already noticed how many car washings it is saving me from. Really reduces the dust and stains if you use the cover religiously when you park at home and/or work. May possibly reduce damage from very minor impacts (e.g., like from a small branch or neighbor kid's soccer ball hitting the car). And definitely seems to eliminate the problem of bird droppings.
<Surprisingly, I haven't noticed any droppings on the cover itself, which has a dull finish. Is it possible birds choose to void themselves over shiny surfaces (like it was over water)? I know birds do avoid defecating in certain areas (near a nest) to avoid predators. Around here it is crows, scrub jays and, believe it or not, hummingbirds.>
Downsides? Like all full-sized car covers, it's big. A few minutes to install or remove. Nighttime cats like to (territorially) spray at the bottom edges and/or sit on on the giant cat pedestal. Let them. The car's interior still gets very hot in summer (I'm in the California Central Valley), but probably not as bad as without a cover. Also, it maybe nullifies some Sentry Mode functions--video cameras? (However, the SM alarm still works with cover on. Found that out the hard way.)
I haven't tried washing. Probably let winter rains do that.