So far, we really only have one model, the basic 110hp LeRhone 9J Nie 17C, with two variants - Vickers and Lewis. Our Noop 17 also masquerades as the 17bis, 23, 24, & 27. It would be lovely to have the others, and if Winder or Pol crank out a few more
clones
of themselves, or if another modeler magically appears bearing gifts, we could have them.
There was a Nie 17B: ten of them were delivered to the RNAS. It was actually an Nie 21, equipped with the 80hp LeRhone 9C - but for some strange reason the RNAS called it a 17B.
The 17bis was the first Brit two-gun fighter; however the only British unit on the Western Front it equipped was Naval Six. It used the 130hp Clerget 9B, and had a deck mounted Vickers and Foster mount Lewis on the upper wing centre section. As Rabu noted, (and skinned), it had a fully faired fuselage (the longerons clearly visible), and the wings were not swept back as on the standard 17C. It turned out to be a bit of a dog - the extra weight of the second gun impaired performance.
The 23 was a later variant of the 17, usually sporting the 120hp LeRhone 9Jb. You would be hard pressed to spot the differences - very slightly different cabane and wheel struts and cowl. The only thing you might notice was that the French version had it's deck Vickers offset a few cms to the right, but of course British machines carried the wing-mount Lewis, so there really were no visual cues to Brit machines.
Cheers,
shredward