By TECHNICALLY, I believe you're asking for some factual substantiation. That's hard. I guess by the purest of definition, you need to be putting the OEM plug into it as that's what it was all designed around. However, I think it's pretty well-accepted that the OEM wires weren't all that great, and that replacements do have a positive effect, so maybe the factory isn't the last word.
IMO, I think plugs like the plus 4 work better in a modern vehicle that runs a much cleaner combustion process and uses a more sophisticated ignition system (higher energy, multi-strike). As I posted in your other thread, my best results have been with the Bosch Iridium and the Champion Double Platinum. If you have a dirty-running engine, with cheap wires, worn rings, etc, you'll probably get the best results with basic copper. It's all about the best path to the spark cap and none of those materials is a better conductor than copper. The E3 is a pure copper electrode.
Your thread title and the topic of your post differ- you ask about wires, then plugs. I assume you're looking for feedback on both.
On wires, I was unaware that NGK made an 8mm set for the Rover. They're OEM replacement is just that- equivalent to a wire that can definitely be improved upon. I like the STI- I think it's the best bang for the buck. I would certainly concede that a wire like the Magnacore is better, but the Rover doesn't have the current to take advantage of it. Can't comment on the third option.
I don't know much about spark plugs and wires but this is my experience.
I bought new NGK Platinums, it ran good, I swapped over to the Bosch Iridium and it ran like silk.
Don't know much about wires either, I bought the NGKs online and 3 of them already broke where the metal tube goes into the spark plug. That being said they're a nice color but they're junk in my opinion. I'd go with STIs or the Kingsbourne, I don't know how much better they are but hopefully better thank the NGKs
It all falls into the category of "you get what you pay for". The caveat, though, is "how much do you really need". The NGK is an OEM replacement. That's not "equivalent". It will do the job of the OEM, but not last nearly as long or have the same structural quality. The OEM is very high quality, but electrically inadequate. The truck doesn't run bad with therm, but it can run better with other options.