I'd delete BG Neo8 from your short list, HiVi RT8-II, HiVi RT2 {if PT2B is lower in cost}. You should be able to use G1-G3 ribbons.

I operate my PT2B @ 1700hz, 8th order. Works fine.

>>I need help choosing a tweeter for a line array project.
I would use PT2B in the low priced range, maybe Neo3 in the mid-
higher priced range, and Fountek NeoCD2.0 for a high end design.

Lets assume a 65" tweeter line. [one channel]

1. Eight PT2 = ~ $200
2. Eightteen BG Neo3 = ~ $700
3. Eight Fountek NeoCD2.0 = ~$950

I would probably bypass BG Neo3 and pay extra for the Fountek.
Neo3 is a lower sensitivity and lower impedance driver than
hinder maximizing line array SPL performance.

You might be able to operate the $4 Dayton dome tweeter at 2khz
with a 8th order or greater crossover. Worse case, 2.5khz will work.
You could add that to your list.

If you want an esoteric line array, then use Fountek NeoPro5i,
the higher end AC ribbon, or R3.2.