One of my Kate's is in kind of a corner near MC, behind a pole. I could stand there all day and no WM employee would likely notice me. However I usually check behind me every transaction, if anyone is waiting I go window-shop and come back to it after they leave. Only one time I stayed there the whole time, when I needed to dump 13 MGC I picked up from the OD sale.
The other Kate I wouldn't do more than maybe 4 at a shot.
With cashiers, if I'm liquidating $200 GC I'll ask for $400 as 2x$200. If they ever asked me about it, which they have not, I'd say I am depositing from my own account and a joint account with the spouse.
That's about my limit. I do try to keep a low profile. I always have my bank debit card handy to present in case they ask to see a card.