Hi,
oil gauge
teeing to run a pressure switch.
switches are set for 7-11psi.
gauge wasn’t very detailed at lower pressures, but I reckon it barely pushed 7 before switching. Likely around 5,
Depends. Your photo. shows you're testing a pattern switch, not an original Smiths. If that pattern switch is NPS thread, it's sold as a replacement for the '74-on switch, which Smiths supposedly rated for 3 psi ...
at revs it’s can be in the 50-80lbs, and in the 20-25 at idle. Given this would it be that bad an idea to fit a generic switch more suited, say one preset for 20psi… ?
It would be a bad idea, unless you want to be freaked after every spirited run in hot weather ...

then the pressure can fall well below 20 psi, although still be perfectly-adequate.
The whole idea of oil pressure switches on Triumphs and BSA's was a mortally-stupid one, because no-one actually knew how widely the oil pressure varied between hot tickover and cold maximum.

Cue dealers inundated with punters complaining about oil pressure warning lamps flashing at tickover on their new bikes; strip-downs rarely if ever found any lubrication-related problems; cue the factories fitting lower- and lower-pressure switches ... 😖 Otoh, if a twin runs 50-60 psi above about 3,500 rpm when hot (and a triple 70-85 psi), if an OPW lamp switched by even a 20 psi switch comes on when the engine's above that 3,500 rpm, the engine's donald already. 😖
If an engine maker's going to fit an oil pressure switch, far-and-away the more-important manufacturing requirement is consistently-good oil pressure at all rpm for hundreds of thousands of miles in every engine made. For this reason, engine makers apart from Meriden haven't fitted feeble plunger oil pumps for decades,
If you're running an old Britbike, knowing you'll never have consistently-good oil pressure at all rpm for hundreds of thousands of miles, if you must be able to monitor pressure in real-time, only a gauge works. However, then you must learn what the gauge is telling you - e.g. after the aforementioned "spirited run in hot weather", the pressure from particularly a twin's weedy oil pump will be lower than what even the Triumph workshop manuals say. Is it a problem? Only you'll know by stripping your engine ...
Hth.
Regards,