Your Atom should probably be OK with 2-3m of the VdH cable as it looks like the normal figure 8 type construction - I would lean towards 3m though to be on the safe side. Whether it will be the best sounding cable here, I really don’t know.
FWIW, Naim’s NACA5 is at least a known quantity, known to work extremely well with Naim kit, and won’t cause any issues with the power amp, provided you stick with Naim’s recommendations on length and termination.