Things are coming together. I'm almost committed to using a 60-Amp
breaker for my subpanel. Maybe it's obvious to everyone else, but it
occurred to me that one doesn't want a breaker so big that the breaker
on one's main panel, in my case 200 Amps, has ANY decent chance of being
overloaded--and thus leaving folks and their tools in the dark.
My shop will have lighting serviced by each panel.

Salesfolk at two different BORGs tell me that 6-3 nm-b romex cable is
suitable as a "feeder cable" for 60 AMP service, even though the charts
indicate that it is only suitable for a 55 Amp device. I would not put
circuits greater than 30 Amp on the subpanel under this configuration.

I have 2 questions I would appreciate opinions on:

1) Is the 6-3 Romex cable suitable for a feeder cable as described?

2) I noticed this cable appears to be 3/4" in diameter. What is the
minimum hole size I would need to bore though studs to properly
accommodate it? Is just big enough to get the cable through big enough?
I don't even think I need additional cable clamps besides for those on
the panels as I would consider if the panels were any further apart.

Thank you!
Bill