I think a torque wrench on a nanoVNA is overkill. The ringing I observed was well above the maximum frequency range.
The issue is getting *consistent* connections. Any time you change the sweep parameters you need to do a cal. I think that some means of ensuring more consistent connection torque is needed. But a "finger wrench" should be adequate.
There would be no way to answer your question except by repeating the same measurement many times.
I plan to knurl and slot a small disk of steel or brass rather than put plastic disks on all my SMA connectors. That's just personal preference. A small square or triangle of steel with an 8 mm hole drilled in the center and a slot 8 mm wide cut to the hole should be entirely satisfactory. A 4 mm lever arm is rather short and lots of SMA-M nuts are very smooth.
Have Fun!
Reg
