I have a used Baldor, 1/2 HP, 7 and 8 inch wheels, it works like in a dream. Super quiet and smooth turning. Very solidly built from cast iron, cannot be compared with stamped cheap grinders. I am sure that with my typical use, it will outlast me.
I don't know about the direct answers to your questions above, but I will say that I got a Jet brand 8" bench grinder from a local hardware store which normally sells to building contractors. It had been sitting in the window long enough so the box was noticeably faded, perhaps ten years or so. It was the only one which they had.
I was uncertain about the Jet brand, but it turned out to be a very nice, quiet grinder, with very well balanced wheels. It takes nearly forever to spin down after I switch it off, so the bearings are quite nice as well.
And -- it spins up almost instantly, so it is not one of those underpowered motors in an oversized housing as so many of the cheap bench grinders turn out to be these days.
I don't know whether a more recent Jet would be as good.