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.