You should definitely keep power and Ethernet separated as much as possible, to prevent inductive loading of the low-voltage Ethernet from the high voltage/current A/C. In building code, low voltage cannot run parallel to high voltage.
We get rid of cable slack by buying 12", 18", and 24" power cables so we can use exactly as much cable as needed. Ditto for the Ethernet side, though usually there's some slack to take up there. So in those cases I loop the cable at the server end and zip-tie them, making sure not to make the bends too tight -- say 3/4" loop where they bend.
For us, the KVM is more problematic, because our KVM supplier stopped making the 2', 3', and 4' cables, so everything is 6'. But, same sort of thing, loop at the server end.
We use the 3M "command adhesive" loops on the sides of the racks to keep the wires tidy off to the side. These work very well, fit in pretty much any cabinet, and are relatively cheap.