I couldn't find old emails, but looking through stuff refreshed my memory..
I regard KH as a botique sample maker... Things have changed a lot and in a bit of a haphazard manner and not everyone will even have the same dir folder structure on the dir system after interacting with Kirk a few times directly. (shrug)
TVEC3 consolidated the various articulations and section sizes into a single keyswitched instrument accessing samples in a way that previously required you to figure out which specific NKI to load for each articulation or section size or variation.
TVEC4 basically is a lot like TVEC3 but adds a pattern editing and playing mode, I think maybe a better way to edit the micro tuning capabilities. Maybe some other minor stuff. Same basic instruments though. This was originally made for CS2 and CB2, but later back ported to Diamond customers for a fee and then later he just started throwing it in with Diamond for free.
The
ESA version of the Kontakt interface later added an Easy Arranging mode, but to my knowledge this did not come with Diamond, it only came with CS2 and maybe CB2. Also some Accent and short note dynamic variations and switchable possibilities.
Diamond comes with strings and brass that originated in the old Ruby and Emerald products and sample sessions, just like woodwinds. He later tried to pull out those strings and market them as "Concert Strings Legacy" in a standalone product. ..its all kind of confusing how Diamond evolved over time..but anyway Diamond basically has all the old stuff.. To my knowledge, these do not include the ESA interface mentioned above, at least they are not in my Diamond download from 2018. But Kirk seems to make custom downloads for people, so your mileage may vary.
CS2 and CB2 definitely have the ESA interface available, they are also completely new string and brass samples compared to what's in Diamond, and according to kirk all new basic programming in how they work, etc...in other words...supposedly improved instruments...not just because they have TVEC4 or ESA front ends, but also the underlying instruments are just superior to the old stuff in Diamond, which actually originated from real old sample sessions a long time ago and then just evolved into a nicer and nicer Kontakt NKI ui...called TVEC4.
Woodwinds finally got a TVEC3 faceplate added fairly recently, same basic instruments and samples underneath, just more consolidated into a single NKI instrument. KH woodwinds are not known to be particularly great, so whatever.. These are the same woodwind instruments as from 15 years ago Ruby and Emerald. Just a bit nicer TVEC3 UI to use them.