I'd be surprised if they were weaker. They're definitely heavier and they going smashing into the curbs every lap which would suggest they're stronger.
Despite them being marked/recorded as magnesium wheels the magnesium content must be so minute as to make no difference and the sheer amount of metal in the wheels themselves only add up to them being pretty bloody strong.
Though as mentioned it means they're sadly also quite heavy, I loved how they looked on mine but they didn't do much for the car in terms of performance.
I believe the reason they have the small spacer on the front of the cup racers is for clearance on the strut if they go low.
They have a coilover so when wound down can run close to the spring collers.
The hubs are exactly the same as standard road car set up, the only differences on the front set up are the lower arms, no rubber bushes, all rose jointed, the anti rotation links are slightly longer as are the steering rack ends (longer).