I do not like to use a grinder as slow as 1750 rpm. it just seems to wear
away at what I'm grinding rather than cutting it off.
The $40 model you mention should serve you well unless you have a monumental
amount of grinding to do.
Finding the right wheel is a bit experimental until you can match your work,
your skill and the wheel all up together. I prefer a medium course on one
side and a medium fine on the other side.