DP Gel and P21S Gel are both safe on all wheels.
P21S Gel is the clingiest gel wheel cleaner out there, and it's what makes it so expensive is that it's super gentle yet SUPER effective. The only downside to the P21S Gel (aside from being absurdly expensive) is that for severe baked-on brake dust such as on the wheel barrels, you may have to spray and then wait for up to 2 hours before agitating with brushes and then rinsing off....the longer you let it sit, the more cleaning power you get.
Personally, I always have a 5 liter jug of P21S Gel, along with various other wheel cleaners for regular maintenance cleanings. The P21S Gel canister is hanging on a wall in a casing that says "Break glass in case of emergency."