If you don’t tow then a tow bar for bike racks on modern cars seems to be disproportionately expensive. A good roof set up for four bikes costs the same as a ball mounted tilting rear rack for four and then you can add the tow bar price of a few hundred (especially if you have parking sensors and it can’t just be crimped into the loom).
Boot mounted racks are all very well but the number plate and lights need to be visible or you need a lighting board so you at least need some electrics tinkering with to give a connection to that and then you can’t get in the flipping boot.
After years of a mix of roof and rear mount I’ve given up on the latter partly because of the additional cost of entry and also rear visibility and access. Mind you the car roof is coated in mud….