I wear long sleeve SPF shirts and then shorts with SPF sleeves over my knees. Sometimes I even wear 3/4 pants, specifically the ones adidas makes for soccer. I feel like loose flowing clothes keep me cooler than sunscreen. I ride during the business end of summer in Texas.
I also recently discovered Prana Hybridizer joggers for MTB riding. I have to wear full coverage because of poison ivy. Anyway, I discovered they are great for air flow and might even try them on road rides. They provide SPF protection but have tiny perforations.
I’m kind of a nut about sun protection because family cancer histories and my own skin cancer scares.