I tried now removing video-modesetting and video-hybrid-intel-nvidia-prime and installing video-nvidia - it does not help. However when I remove all three of them (i.e. no graphics driver installed according to mhwd) the modprobe service doesn’t restart anymore continuously and the stuttering stops. From the power consumption reported in powertop it also seems that turning the dGPU off with bbswitch still works. Obviously I cannot run programs with prime now anymore, but I don’t really use it on linux anyway.
I guess this resolves the problem, thank you everyone.