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A 2" wheel is useful if you want to hollow grind. The easiest approach is to first grind the razor using a larger wheel, and when the bevels are ok, you switch to the smaller wheel to scoop out more...

You need variable speed for post-H grinding which is the most heat sensitive step.
Without speed control, you'll burn up razors. Also in terms of wheel size, I find that 4" is the size I use most....