We toured for 10 days down over the Swiss alps to Tuscany last year.
Most clothes can go on the hooks behind the seats - use suit bags to protect from dust or getting caught in a rain shower.
We then had shoes in the well of the boot, wash bags etc pushed right to the back, and soft bags - still space for camera stuff, coats, wine, etc.
I thought about a boot rack but decided it was less safe when parked up and honestly never missed it space wise.