Re. the dress uniforms introduced during Insurrection; I would regard them as a wholly separate development from the TWOK officers jacket to TNG dress uniforms. I have also wondered at times whether those uniforms were intended as 'mess dress' uniforms. That is; the military equivalent of evening dress; and were separate from the TNG dress uniforms. Clearly that is what the design is based on (the outline of the white bits is obviously very similar to the outline of a military mess jacket).
Maybe. We've only seen them used like...three times, once in INS, again in NEM and once more on DS9. However, they were used in situations which, previously, the characters used dress uniforms (e.g. O'Brien vs Riker-Troi's wedding).
The fact they the INS dress unis were a dramatic departure from the previous outfit isn't unprecedented. The TOS dress uniforms were quite different from whatever followed. Though, now that I look at them, the elaborate TOS-D collar could have evolved into the WOK collar and the zipper in the middle moved left into the WOK flap.
http://tos.trekcore.com/hd/albums/1x11hd/themenageriepart1hd601.jpg
Odd that they didn't include rank stripes on the sleeves of the TOS dress unis. That makes zero sense. Might have to chalk that one up to 60's corner cutting rather than intent.
As regards enlisted crew in the TWOK era; I don't know if they would have had as many options as officers: to give a real-world; present-day parallel, in the Royal Navy today, junior rates (everyone below petty officer) have only three uniform variants or 'orders' to choose from: 'number 1's' (sailor suit-worn for formal occasions); 'number 3s' (short sleeved shirt worn with smart trousers, no tie and an optional jersey-for semi-formal occasions) and '4's' (utility, everyday wear for everyday tasks)-whereas senior rates and commissioned officers have the added options of mess dress and more variety as regards their semi-formal dress. And Admirals have even more variety; adding a 'ceremonial day coat' that is essentially the same as the uniform worn in the days of Hornblower, (had he been real of course, but you know what I mean)-only a peaked cap is worn instead of a cocked hat. And that's without the white tropical versions of these uniforms. And this disparity between ranks is true for most armies and navies throughout the world. The main reason being those at the top have more money to spend on more varieties of special uniform (not to mention the social connections one would need for wearing mess dress for example)
We can only speculate as to whether or not enlisted crew had any kind of dress uniform. Given that Kirk & co stood in front of the Fed president and full(?) council in their "normal" uniforms in TVH suggest that there was no dress uniforms for officers beyond what they wore on duty.
Related WOK question: at what times did they ditch the turtle necks for the Tapestry t-shirt and what time frame could they have dropped the t-shirt for none at all.
TUC, GEN and VOY:Flasback took place in 2293 (busy year) and all used the full WOK outfit.
Tapestry's "past" events took place in 2327 and had ditched the turtleneck.
1701-C was lost in 2344 and had no visible undershirt.
Am I missing an episode?
The aborted Generations uniforms were indeed very TWOK-ish, I agree. Shame they weren't used in any form for the film in my humble opinion, even if just s dress uniforms.
I think that was deliberate to better draw a connection between the prologue on the 1701-B and the rest of the movie. Apparently, the TPAB yanked them at the last second (which is why the GEN Playmates action figures have the aborted uniform, too late to change production) and that they were intended to be the uniforms for Voyager (to keep them distinct from DS9).