Do a search in this forum with Royal Purple and the Redline in the subject line and you will find 256,590,875 posts.
RP xw30's have a tendency to shear. I would use RP 5w40 in a tuned WRX in So. California, or Redline 10w30 or 5W40. Do a used oil analysis to determine the appropriate oil change interval. Doing a search with "Redline" should show you a result of a recent uoa on RL 5W40.
RP is API certified and RL is not. However, do you have a powertrain warranty anyway?