Am I correct in thinking the 20v Turbo has a lower suspension set up, compared to the 20v NA? Checking the wheel/tyre sizes:

20v Turbo 205/50R16Y (radius 305.7mm)
20v NA 205/50R15W (radius 293mm – 12.7mm smaller than the Turbo)

The Turbo would end up with an additional 12.7mm ground clearance, if the suspension set ups were identical.

I was looking at getting a 20v NA, but fitting the 20VT wheel/tyre combo, but I’d have to lower it, to retain the same ride height, right?

I think even with 20VT alloys the n/a is lower as, infact, the n/a has the lower setup. And you can fit whatever wheels you like. And it sounds nicer. My wife had one for a while and it was lovely to drive - more than made up for the relative lack of grunt. Get (a good) one.