Piling on! Newbie here who started lurking on bikeforums to learn about my '79 Vista Espada mixte.

Found the specs page of a '79 Vista catalog and everything listed for the diamond frame seems to match up w. my mixte:
-Araya 1435 tubing
-Dia Compe brakes w. turkey levers
-Suntour Powershift stem shifters
-Suntour VGT-Luxe RD/Compe-V FD
-Sugino 165mm cranks

Accidentally traded away my original steel wheels+freehub for lighter aluminum before I understood anything about compatibility, and the 5 speed freehub that's on there now isn't playing nice with the Powershifters. I'd initially assumed they were regular friction shifters, but no. The ratcheting intervals on the downshift don't line up with the gears, so downshifting is a pain. I usually shift a gear or two past where I need to, then use the friction shifting on the upshift to get it into the desired chainring. Suntour 5 and 6 speed freehubs are available on eBay, so I think I'm going to try to get a vintage replacement. The 5 speeds seem to be a bit more common though, so I'm trying to figure out:

a) Do vintage mixte components usually match the diamond frames of the same model? The spec sheet lists the diamond frame as having a 14-28 6-speed, but my husband swears it came with a 5 speed, and this bike seems to have been entirely original when I got it.
b) Does it matter? I'm intrigued by the Powershift shifters, and want them to work as intended. My impression is that it's the Suntour gear spacing that's the compatibility issue, not necessarily the number of gears. I've seen a number of 5 speed hubs that look to be in decent shape, and wouldn't be mad about having a 10 speed bike instead of a 12 speed...

Any advice/info appreciated! (And/or suggestions as to where else I should post this question)

PS--No photos allowed yet because I'm a newb, but will come back and post photos of said mixte when I've made the requisite 10 posts.