I use one of the Halfords ones (cost about £80 for a full-size one) on mine. It works very well, and breathes quite well too, but I take it off every week at least. I let it dry out (both the car and the cover) then put it back on. Never had any problems like that, not noticed any ill effects to my paint either.
If stored in garage get a dehumidifier with auto sensor so it kicks in when it needs to and then set up a outlet for the water to drain outside,ive used one of these for years in my garage and what a differance it makes and keeps the car very nice and no damp smelletc ,as i got caught out with covering my car in my garage and had real bad paint issues due to the moisture in the air
Keep my car in a garage with no cover on, let it breath is best.
A dehumidifier helps if your garage is prone to damp..