If I had an allergic reaction o Sculptra, how likely to have one to Voluma?

Voluma is an HA filler while Sculptra works very differently. So there is unlikely to be an associated allergic reaction, especially if you've had Juvederm in the last two years. If you are concerned you can consider having a patch test done to check for an allergic reaction.

In my experience, allergic reactions to Sculptra are extremely rare. That being said, Sculptra consist of poly-L-lactic acid while Juvederm and Restylane are made of hyaluronic acid. Since you have had Juvederm in the past without issue, I suspect you will not have an allergy to Voluma especially since allergies to HA fillers are rare to begin with. I prefer to use Restylane Lyft over Juvederm Voluma when treating the cheeks. In general, I prefer the Restylane family of fillers over anything using Allergan's vycross technology. 

I doubt very much that you had an allergic reaction to Sculptra. Most likely the problems were secondary to the technique that was used or insufficient dilution of the product. Regardless, you can easily have Voluma used on your face just make sure you go to a plastic surgeon who is well-versed with a the is of volumetrics. Good luck from New York City