Stick with metal and bolts with backing plates rather then screws. There are a lot of them out there. Rocker guards, corner guards are pretty basic. Then you get full length corner guards that integrate with the rockers, giving you a more complete protection. Although unless you're doing some hardcore off-camber crawling, you probably don't need to go that far.
Yes, your paint will get fade lines. You'll also end up with holes BUT you don't usually take the panels off so you shouldn't worry about them.