Hi Paul and welcome to the club.
It is a refreshing touch to see you have joined as a proper paid up Z club member before getting your car. Shows you in a very positive light in my slightly old fashioned book
I think a lot of your opinions may have been formed by reading too many US forums.
There is no S1/S4 - a small minority of mis-guided US (enthusiasts ?) may try and claim such, but that is not anything officially recognised anywhere.
There are only production changes, some were improvements in the manufacturing process over time and others were perhaps mostly backwards steps designed to combat changes in US federal law ie bumpers that became progressively larger, carbs that were a stop-gap solution pre-injection etc.
On US forums they generally have a myopic view of the Z in referring only to the HLS30 model particular to their market, which was a pared down lower specification S30 model sold only in the States with 4 speed box, inferior steering rack, 3.364 diff ratio, softer springing, no rear arb etc
In the US market an early 69/70 HLS30 is more desirable..ergo collectable..ergo expensive but not so revered elsewhere although it seems some of our Euro friends are in danger of getting sucked in. I think this is a fairly recent angle and possibly pushed by investor types wanting to hype prices. It was true that by 1973 the stock factory cars offered over there were much less sporting than the original cars and laden with emission equipment, de-tuned carbs, lower compression, heavier bumpers etc and 0-60 times of over 10 secs but how many survive in that trim today ?
Like for like, in the UK an original rust free or nicely restored HS30 rhd car (of any year) would be more desirable and valuable than an early HLs30.
Most cars will have had changes to their original spec. and perhaps HLS30 cars more than any others due to their inferior factory spec. This is the beauty of the s30 model lineage.......engines, boxes, diffs easily inter-changeable, upgrades to steering, suspension, brakes etc very common so chances of any two cars having the same spec. pretty rare.
In terms of how they drive in factory trim, the 240Z offers the most basic, raw and connected experience with the later S30 cars offering a slightly more comfortable and sanitised experience.
The 2 seater 260Z RS30 is also less common than the 240Z with about half the number sold here new. Price wise hard to say and like/like comparisions difficult as so few genuinely nice cars come to the market but would say the RS30 260Z is slightly behind the HS30 240Z but not by much, maybe 10-15%.
Firstly decide on your budget (which may dictate your options) and then don't get too hung up on whether 240/260/280Z. If HLS30/RLS30 is OK for you it opens up a lot more opportunities. There is inverted snobbery and a top trump pecking order with all classic cars/marques, the John Cleese, Ronnie Barker, Ronnie Corbett sketch springs to mind. Just ignore it and do your own thing.
It goes something like this, 240z is better than 260Z is better than 280Z is better than 2+2 of any kind is better than a ZX ooooh but hang on, what about the ZX turbo, oh yeah, but I've got an early vented hatch 240Z, ha ha well I've got an earlier vin number, well mine is in the rarest colour, I've got a 432 trumps you all ........... and so it goes on. Now I've got that off my chest, what was your question again ? You did write a long piece for a first post