I largely tend to agree with Philbert on this topic. Get a decent quality grinder. Wheel changes are a 30 second affair. No need to over think it. Dress the wheels between chains. Let the wheel do the work and don't force it. As with everything there's a learning curve, and I wouldn't let just anyone use a chain grinder. It's really easy to screw up a chain beyond usable in a hurry. Don't worry about reversing the motor.
There are "better" wheels you can buy that won't need dressed, but they cost quite a bit. I've worn out a handful of wheels in the 10+ years I've had a grinder, even doing chains for others.
Not sure where the pure sine wave bs is coming from, it's a basic motor, any old generator will run it just fine. That's only a thing for sensitive electronics. Which none of the mentioned grinders remotely come close to.
I'd advocate some carbide chain (s) if you're really getting into nasty/ demo style clean up. Yes, they cost an arm and a leg, and yes they need sharpened with a diamond stone, but they will keep cutting a lot longer then a regular chain in hard conditions. Killing a few regular chains pretty much evens out to one carbide chain cost wise, especially on longer loops. Just a thought, and yes I understand they arnt practical for a lot of reasons, but they serve a purpose.