The essential philosophy was to bring the original UI from WH1/WH2 into the third game and give the WH3 factions UI with similar feel, which I suspect was the original plan but then CA changed course at some point, for an inexplicable reason.

It is completely beyond me why CA decided to ♥♥♥♥ all over what they made in two previous games and replace it with something, in my opinion, completely inferior and scuffed.

I tried to stay as faithful as possible to the reference (two previous games) while preserving new WH3 UI features.

WH1 and WH2 factions have more or less the same UI as they had in the two previous games. WH3 factions now have an equivalent of that with recolored assets from the other two games into the bronze/rust/gingerbread color palette with parchment slightly burnt on the edges. Components that are completely new (Chaos Gifts, Ice Court, Formless Horror etc.) are completely left as they were.
The only exception to this are Warriors of Chaos as they got a large overhaul with Champions of Chaos DLC. The three original legendary lords (Archaon, Kholek, Sigvald) are where the old and new meets - the original UI components have WH1 golden skin mixed together with the new, bronze/rusty components and I'd say it looks pretty decent. The other WoC LLs have the regular WH3 UI.

Main menu has also been slightly changed so it's slightly less dark and the lord selection movie doesn't get horizontally stretched anymore (especially noticable on biggers screens).

I don't play multiplayer, therefore I have no idea how the game is going to look in MP. Probably slightly screwed so bear that in mind.

Living World - excellent mod reshuffling starting positions in a loreful way, making campaigns more interesting and playing factions like Reikland less masochistic
ULTIMATE LIGHTING 2.0 - nobrainer. Makes the battles look better overall and eliminates the dumb vanilla blur of distant landscape
Campaign Weather Overhaul - probably not everyone's cup of tea but I enjoy this one as it makes the game feel very loreful. However, some may find the omnipresent fog too obtrusive
Better Sound Levels Mod v5.4 - sadly, not only UI got scuffed and this mod fixes a lot of it. Makes the game feel much more immersive
Guns, Smoke & Spectacle - if you really like gunpowder
3D Porthole Lighting Fix - excellent mod to make portholes not vomit inducing
Points of Interest with Pictures - a nice flavor mod
Less buff and effect VFX 3 - less visual clutter in battles and better spectacle
Softer Corruption Graphics - because vanilla is meh
A very personal recommendation - while the WH3 overall looks pretty dark due to the vanilla dark UI and increased campaign map colors saturation, some genius at CA realized how dark the entire game is and decided to increase the gamma by 10% and then completely remove the option from the game. You can notice this by direct comparison of WH3 with my mod and WH2 and see that WH2 UI looks darker/more saturated. For this reason, I use a simple reshade filter.
If you wish to achieve the same, download reshade, turn on LiftGammaGain filter and move RGB Gamma value from 1.000 to 0.900 and the UI should now look the same as in previous installments.

Visual part:
u/LordChatalot - for giving me the initial idea by starting his work on parchment UI and then pissing me off by not finishing it which motivated me to start this
ChaosRobie - for making Before the Shadows campaign, which made several hundreds of my game loads significantly faster
Groove Wizard - for a bit of brainstorming and introducing me to LUA UIComponent wrapper
prop joe - for creating the amazing mod manager and the dev console, making play-testing much easier
Frodo45127 - for making RPFM without which making this would be hardly possible
Tomasz Wegrzanowski - for making TWUI -> XML converter without which directly replicating some stuff such as animations would be impossible
Müsliriegel - for giving me the permission to steal a few of his assets from Unique UI mod and saving me a bit of time

Audio part:
Audiokinetic Inc. - for providing me with Wwise non-commercial license
Pear - for guiding me through the process of putting new soundbanks into the game
Ole - for active development of Asset Editor Audio Explorer
Makers of wwiser, vgmstream, and foobar2000.
Groove Wizard - making LUA console that made sound testing much easier
prop joe - for creating the amazing mod manager and the dev console, making play-testing much easier