re: Denver airport: national car rental company vs. Turo

Become a member of the program you choose, and make your reservation directly. I have never used Turo.

With rentals and hotels, if there is a small discrepancy between your rental and your ID/CC, for instance, it'll make you go to the counter (John vs. Johnny). OTAs (CrapPedia, SliceLine, etc.) increase the risk of that happening, and when you arrive late, there will be one or two people at the counters working multiple people that also came in on your flight.

I flew into DEN a few months ago and sat for more than 20m having to wait in line (at the Avis counter, after a 20 m wait/transit/wait from the terminal), because my company travel portal left a letter (I think) off of my full first name, which threw a flag which killed my ability to walk straight to my car. That was Avis (I've had an Avis profile for 20 years.)

Anytime you fly in and need a rental car when a manager isn't on duty (probably after 1800), just assume that you're not leaving the airport within 30 minutes of collecting your baggage. You might, but you probably won't.