Pubic Auctions are not for the faint of heart, those with limited knowledge or limited means.
As noted, Off Lease and the Best cars go to Dealer Only auctions, leaving the Repos, High Mileage and problem cars for the Public.
That’s not to say that you can’t find a good deal at a Public auction but it will probably be an older, low demand, high mileage and needing some cosmetic repair vehicle so you’re taking your chances.
i.e. A 5+ year old one owner Buick or Oldsmobile sedan with lots of parking lot rash would probably be a better bet than any SUV/Pickup/Luxury/Sports vehicle that can be easily sold by a used car lot.
The next consideration is the type of auction. Some like Mannheim are mostly commercial auctions so they tend to get the better vehicles, provide more pre-auction information and generally have less risk.
Others will will literally take anything that can be dragged to the line so you’ve really got to know what you’re doing. Again, you can occasionally find some good deals but again stay away from the above categories which are usually bought to be shipped to the Third World where repair costs and standards are much lower.
My suggestion is that if you’re not experienced and going the auction route, that you find someone you trust with a Dealers license to do the bidding for you on a commission basis. It’ll cost you some money and it’s still not risk free but it’s an easy sale for them and increases your chance of avoiding a turkey.