There were a few small economies introduced into the rifles produced in the '20s and '30s, compared with pre-WW1 production (ie. pressed steel trigger guards). But I can't see a great deal of difference in fit 'n' finish between any of the pre-1939 BSAs. The quality of materials and workmanship was extremely high in all.
Re. slightly leaky taps, I'm not convinced it makes a huge amount of difference to either power or accuracy, so long as the breech and barrel are properly aligned.
IMO a Club Standard No.1 (ie. 1920s, .177) ranks among the very best of all the various BSA models produced from 1905 onwards, although I do have a soft spot for a straight-hand stocked version of the 45.5" Improved Mod D (built from about 1909).