Hi! The standard for spacing around inset doors and drawer fronts is 1/8” on each of the four sides (and 1/8” gap in between two adjacent doors).

There shouldn’t be any rubbing if the doors, drawers, and openings are made very square and accurate and are mounted firmly on their hinges or drawer slides.

I think 3/32” would be the widest acceptable spacing I’d allow.

1/4” sounds like too much and would look awkward.

And would you say it’s the correct approach to stick with the standard spacing even if we have uneven floors/shifting/etc.?

Yes. If you can not get the flooring level, then the cabinetry needs to be shimmed because the countertop crew will not install an uneven countertop. 1/4” is too large. We always use 1/8” standard. The soft-close under mount slides have multiple touch points for leveling. Hope this helps. Feel free to contact me directly.