I did plan to use staples on the 1/4" underlayment.
Followup question(s): can I get away with just the 3/4" T&G? I was worried that with all those screw holes, some would undoubtedly telescope through. Maybe, however, I'm being overly cautious. Alternatively, could I fill them in with a patching compound (sanding as necessary)? If so, any recommendations on what type of patching compound to get?
If I should go with the 1/4" underlayment, any recommendations? I've heard that I should avoid luan, but so far, luan is the only thing I can locate in my area. The lumber stores all think underlayment means subfloor plywood. Lowes and Home Depot aren't much better. Home Depot does have the following: