Resist if you are not sure since opening a financing account will affect your credit score. When you request the 24-hour test drive, sales will push you to buy and use the return policy instead. CarMax was started by Circuit City, in '93 I believe (experience). All of them will call you if you did a pre-qualification with them. Only vroom cold called once you registered an account with them. CarMax has an optional 5 year warranty plan. Below are some unrelated notes you may find useful: Overall, I'm extremely satisfied and will return if I ever look for another 2nd hand car.
Since the repair was within the 90 day warranty period, they replaced the brakes free of charge. Also, they provide free Lyft rides, which is convenient so you don't need to wait at the shop. I took it back to CarMax (the one near mine has a service center) and they fixed it in a day.
After a week my car started making noises whenever I backed up. I went back after 3 hours and bought the car. I was able to take it to the freeway and back to my home to see how it fits in my garage. This is another great value proposition most other dealerships don't have that I found useful. The car took about a week to arrive (SF to LA), and I was able to do a 24-hour test drive. The cost of the car transfer is not redeemable upon purchase, but to me, that was a fair price to pay to make sure the car is without "surprises." I did my extensive research between CarMax, Carvana, and Vroom, and although they all offer pretty much the same policies, I chose CarMax because they had more physical dealerships where you can ship the car you like to test drive before you buy the car.