Some users have found that it is a good idea to keep the 2020 drives away from the PC. We install the PC in the same cabinet with the drives, but it is a large cabinet (5' high, 3' wide).
All pulse width drives produce lots of electrical noise. Motor wires should be shielded right up to the connections on the drive although we don't hook up the shields to anything. I know this does not make sense, but it works, and dealing with electrical noise, success speaks for itself. The motor wires (and braking resistors) seem to be the biggest producers of electrical noise, so I try to keep these shielded well, and where possible, I like to see the braking resistors away from the drives/ and PC.
It is important to use shielded motor, encoder wiring and step and direction wiring. Good shielded cables in these areas take care of most noise issues if not all.
Keep the step and direction cable around six feet or less. I order my shielded cables from Microcomputer Cable company in Michigan. They have great cables at very good prices. If you call me on the phone, I'll give you their phone number.