If it is feasible to use NACA5 that is what I would do as it’s the cable Naim would have used when developing the Atom.
However, 1 metre seems very short. Classic Naim boxes need at least 3.5 metres and although the Atom will probably tolerate 1m per side, such short cables might impact sound quality and there are practical considerations. NACA5 is stiff and thick, so I doubt you’d be able to be able to have the speakers much over a metre apart even with the Atom bang in the middle. If you can cope with it in your situation, my recommendation would still be NACA5, but preferably around 3m length.