When will Traktor Pro 4 be fully compatible with the M3 processor?
Right now. TP4 is working on my M3 Max.
Great that it works for you, but I’m waiting for an official statement from NI on this matter.
Are there any relevant differences between M1, M2 and M3?
I can't remember them announcing any compatibility between M1 and M2, or ever on any new x86 generation.
There is only this:
https://support.native-instruments.com/hc/en-us/articles/360014683497-Apple-Silicon-Compatibility-News Which I would suppose counts for all apple silicon CPUs.