I've bought copart many times. What you need to know about is fees and risk.
For fees, anything you buy will come with lots and lots of fees..
$29 to bid online; $59 for the vehicle to pass through the gate. Then there's the sliding scale buyers fee, slightly cheager if you pay by money order. Don't forget sales tax on everything.
Certain states require you use a broker to bid, here in GA you don't unless it's clean title or clean bill of sale. But if you do, figure $200-350 more there l.
Then figure your delivery/pickup costs.
As for risk, well, if there's unseen damage, or something happens while they move the carcass around, that risk is on you. You don't have a "right" to back out or cancel things, and they don't have to pay for the damage. If you make the claims and piss off the yard staff, you are rewarded for your efforts with the difference in value between what that car would bring at salvage auction with the extra damage vs what it would with the original damage.
Oh, and don't expect a spare tire, never received one in the dozens of cars/trucks i had hahaha.