Only book rates you can cancel up to 48h before. plans change, and a non-refundable saving isn't a saving.
βFull-to-fullβ is fairest. Avoid βfull-to-emptyβ. you pre-pay a tank at the depot's price and lose what you don't use.
Check the security deposit they block on your card and whether Full Coverage drops the excess to zero. This is where surprise costs hide.
At pickup, film the whole car. every scratch, the fuel gauge, the tyres. It's your proof against a disputed damage charge at drop-off.