So I have the Ls400... I absolutely love it, and use it every day, almost.
Anyway, I have an important job that requires I lay down the perfect coat of white dp, not heavy or light, just the right amount.
Anyway I have a finex 1.4 and several other lesser guns. I also have a transtar 1.7.
The last thing I want to do is shoot epoxy through my supernova. I'm not 100% certain I can pull off the ideal base for my application with those other guns.
So If you were to buy a solid gun for epoxy and high build only what would you grab?
1.4 or 1.7... High end hf or low end iwata....?
Normally I sand everything up to my base coat or single stage first coat, in this situation sanding is not an option. My skills are definitely up to the task, I just don't want the gun to be the weak link.

What would you do if you had to buy a new gun for this application tomorrow?

You're asking two different questions.

The best gun for non-sanding epoxy is probably a 1.3mm - 1.4mm RP gun with very fine atomisation. The best gun for high build primer is probably a 1.8mm.

Why don't you do some testing? Try each of the guns that you think might do the job and then adjust settings to see what effect that has.

In my kit, the best gun for non-sanding epoxy is, surprisingly, a 1.4mm Star. It is also capable of putting down 2K solid better than the Pro Lites, especially on smaller jobs. Shouldn't, but does.

Nobody can answer that question for you as far as gun type honestly,

sounds like you are trying to hit a mil spec so get a wet mil gauge and do a test panel to see what your numbers are like per coat, then youll know where and how you need to spray.