1. The guidelines are about the size/use of the machine - and OP is clearly trying to stay out of "hobbyist" territory.
2. Grizzly (which also owns the soutbend brand) is a kind of aggregator/distributor of relatively variable stuff. Meaning a model abc1 might be quite subpar while a model abc2 might be quite good.
3. Having dug through that, I bought an SB1012F 14x40 lathe. I'm not a commercial shop, but it gets used by me, a swarm of robotics students, and various of my associates (well, in the before time.) The gearbox can be clunky, and the DRO is a touch coarse, but for what I (we) have done it has been fine. It is nothing like the PRC machines I've seen. Search for that model and you'll find other folks on PM who've had OK results with it. I would think for any business where you are doing repairs, working to fit to another part, doing second ops, it should be fine. But I'm mostly a mill guy.
4. It's quite unlikely that any of the other taiwan machines would be much different. There are no practically priced new machines made in the US so far as I could tell. If you need/want to buy new, you're going to end up with an eastern Euro or Taiwanese machine. (Weiler apparently still actually exists but seems hard to find....)
By the way I'm sick to death of the "buy a good used machine" because that process was just nuts in my area - people who list machines they didn't own, or change their minds about selling at all (let alone price), one ad listed a phone number for some (unhappy) folks who didn't own the machine in question and were befuddled about why their number was in the ad.
5. Having visited the Grizzly showroom in bellingham, yes, the SB branded machines are a higher standard of fit and finish than the Grizzly branded machines (and more money as you would expect), and from what I saw, they *seemed* less variable - that is, I would guess that say a larger or smaller machine in the line my SB1012F came from might be an OK risk.
6. Be sure to get (either in the package or ordered at the same time) any machine specific accessories (taper attachment, steady rest, follow rest) - because after a model change these may be hard to buy. Things that fit to standards (e.g. the D1-6 camlock chucks) don't have this problem.