Sticker situation makes sense: Reynolds couldn't realistically mass-produce a wide variety of stickers in every language. There were a couple of basic stickers: "531 main tubes" (i.e. triangle/"3 tubes"), and "531 frame, fork, stays". I'm guessing they didn't want to double the number of variations by doing separate "frame, forks" and "frame, stays" stickers. In a way your stickers make sense: The manufacturer made the main triangle out of 531, but not the stays, so they used the 3-tubes sticker on it. Then they used 531 on the fork blades, thus marked it as such.

I don't think the variety on bikes was much different from cars once we got to the 60s/70s in that you could easily get a car with any number of options. Pickups of the era, especially those from GM, would come with an options sheet glued to the interior of the glovebox door listing off any RPO codes associated with options/upgrades installed or ported into the vehicle, although they came with the same basic frame. I wouldn't say the cycling world is a direct comparison, but y'know...

The clamps look like those which came with the coveted T.A 213 or more common REG brand handlebar bottle holders, along the lines of:
T.A. (most likely): Specialites T.A. - ref:213 - handlebar mount bottle cage
REG (also possible): https://steel-vintage.com/reg-162-cl...le-cage-detail

There's a few varieties of the same, I've got a couple of these T.A. 213 holders sitting on a shelf in the shop, they were selling pretty regularly a couple years ago on eBay in the $50-100 range.