I use Autoslash to “track a rental” after I’ve got a reservation. It will send an e-mail when the price goes down, which is a great tool, since I’m a price watcher. It gives me an opportunity to rebook at the lower price, and the have Autoslash watch that one.
I have never had an issue with any of the major car rental companies. In the dark ages (80s) I worked for Dollar at the Kona airport (Hawaii) and learned all the tricks - many of them (tricks) don’t exist anymore (like pushing hard on insurance and upgrades), some do, like selling gas in advance (bring it back empty - that is never a good deal for the renter and should only be used in the most extreme times…or by traveling business folks who just don’t care because they aren’t paying out of their own pocket). Things I watch for are cruddy windshield wipers and tire tread wear.