Hi There
I bought a Rexon from B&Q and it seems fine.
6 inch wheels are large enough but whichever grinder you buy, I would change the wheels.
I have fitted mine with A60K5V where 60 is the grit and the K is the bond strength I think.
Long while since I did the grinding wheel safety course.
The bound strength K can vary a bit but you don’t want it too hard.
I got my wheels from J&L.Industrial.
I don’t sharpen carbide in the home workshop although I do have a couple of diamond wheels for when I get the cutter grinder uop and running.
regards David