I've only seen like 10 matches of his so I can only comment on him as an in ring performer. Dude was very good, not sure who I could compare him with though, maybe a way better Lex Luger (and Luger was pretty damn good in the 80's-early 90's)? Not sure. He was indeed an "80's worker" but he knew how to sell, how to make a compelling comeback, good punches, and facial expressions so he should've been fine in the 90's.
I have no clue how he was as a promo and character though. But as you said, it's pretty much a consensus he was damn good at those too.
Don't think the business would've changed with him getting a run as NWA Champ. Though JCP would've given Vince an interesting fight during the years they desperately needed a big face (87' and early 88').