I'd agree with separating power from signals
My machine has echain down either side of the X axis carrying each type.
The machine before this one has some of them together and tripped out quite a lot. The new one is much better but the long Z home cable occasionally still causes a trip.
I must point out that the previous machine and the current machine both use cables direct from the BOB so they end up being long especially Z. How much of this can be improved / removed further by using relays etc I will soon find out because that will be of my electrical upgrade in progress.
Back to your question. I started with 50mm or so but these are quite bulky so latest machine has something like 20-25mm width and is much more compact whilst still taking the cables. Helped by splitting runs down each side as mentioned.