A search of this web site should get you previous threads about clear bras. It is also worth searching the Porsche Cayman site,
http://www.planet-9.com.
After watching the paint chipped off the fronts of several cars, I invested in a clear bra for my G37S. So far, I think it has helped substantially. There are three factors to consider - the material, the installer and the price.
There are several different materials. Mine is 3M. In the past, 3M has been criticized for turning yellow after a few years. Supposedly, this has been fixed. It will be more of a problem for light colored finishes than for my Blue Slate.
You need a good installer. See how they handle edges. The good ones wrap the bra material around the edge of the hood and around the fender wells so that the edges are hidden. The shoddy ones use a sharp knife to cut the material at the edge of the hood or fender well. One slip and you have a scratch in the paint. Even if they get it right, you still have an edge showing. Search as many web sites as possible for leads to installers with satisfied customers.
A competent job should cost $200 to $500 depending on whether they cover just the front 18" of the metal hood and fenders or the plastic bumper, too. Mine cost $350 for the metal parts but included a complete detailing job. The dealer's price for the same amount of work, including the detailing, would have been $1,300. To make things worse, the dealer's installer was one of the guys who trims with an X-Acto knife.
A clear bra shouldn't affect washing and waxing. I'm not a fanatic. A couple of times a week, I hose mine off at a self service car wash. Every few weeks, when the interior starts collecting dust, I take it to a touchless car wash because they vacuum and dust the interior, too. A couple of times a year, after the wax has worn off, I take it back to the shop that installed the clear bra for a complete detailing.