Yeah the braking on bikes is pretty bad, highsides or fishtails if you brake hard, bit better with the controller as you can lightly brake but on m+kb it's all over the shop.To me personally driving is okay in CP2077.
It's worse than Forza Horizon but better than NFS games, somewhere inbetween GTA 4 & 5.
Only the "Bugatti" has weird brakes, the brakes executes only after few seconds after pressing "S". Drifting mechanics/physics could also see some improvement especially with bikes.