Are we talking a VFD setup, or a single speed?
Either way I think SFPM (surface feet per minute) would be way faster then I'd personally, want with a 7" drive wheel.
On my old Square Wheel (my first "real" grinder) which came with a 10" drive wheel, on a 1725rpm motor, if you made even a slight bobble with a heavy grit belt, it would almost cut a blade in half.....and nearly always wreck it beyond repair. With finer grit belts the heat build up was astronomical too. As soon as I knew enough, and before they were ever available commercially, I had a 7 1/4" drive wheel custom made for that machine.... but even with that it was still too fast. (7 1/4" was the smallest I could use without having to extensively modify/built a whole new tooling arm....and at that time in my career, my skills were simply not up to the task).
All that being said, if it's a single speed machine, I'd go no larger then a 6" drive wheel, and if it's a VFD machine, no larger then a 4" drive wheel. The reasons I say that is because I can always grind a little more off, but if I grind too much, I can never put it back. In addition, heat build up during finish grinding, from finer grit belts running too fast, can be a very serious/difficult problem to overcome.
I'd much rather have/work on a grinder that runs a bit slower then I'd like, versus one that runs too fast. The only thing a slower grinder might cost you is a bit more grinding time.....while a machine that runs too fast multiplies problems exponentially.