So should I try the pi5 with the gpio cable or don’t try idk I dotnt have cm5 or waveshare products
Yep, definitely try the Pi5 connected to the GPIO pins - maybe look around the forums for different ideas on how to connect the Pi5 to the Pi-Top GPIO pins.
It will work and I found on the latest version of Raspberry Pi OS the screen brightness buttons worked natively. The only downside will be the Pi will complain about under voltage both as only as you don’t connect any accessories or push the Pi5 it will run.
Good luck!