Will write a better description later maybe. If you look at my profile you can see I upscale a lot of stuff and info, blah, blah.

Pending complete rewrite because I hate myself. (except for landscapes and plants. Landscapes and Plants are (hopefully) final version) They're not because I hate myself too much.

These have mildly technically descriptions and information, some of which is a version or so out of date, because I'm trying to push these out. Essentially just makes things look better without being too different from vanilla.

Cleaned (1x) sets have been moved to 'Old files', because they are Deprecated by CSSET.


Q:
8x for landscape and plants?

A:
No.


This video shows how they upscaled the Skyrim textures. It's not great.


For this mod I use Skyrim LE + HD texture pack + Normal maps & new textures from SSE. For modules I will define into two catagories: Mostly HD and Mostly Original.

Mostly HD:
Will be mostly:
4x will be max ~8k textures. 2x will be max ~4k textures. 1x will be max ~2k textures.
4x will be 4x of SSE textures. 2x will be 2x of SSE textures. 1x will be 1x of SSE textures.
4x will be 8x of Original Skyrim. 2x will be 4x of Original Skyrim. 1x will be 2x of Original Skyrim.

Original Skyrim means Skyrim Legendary WITHOUT HD Pack.

Mostly HD pack:
Clothes
Armor
Weapons
Clutter (soon)

Mostly Original:
Will be mostly:
4x will be max ~4k textures. 2x will be max ~2k textures. 1x will be max ~1k textures.
4x will be 2x of SSE textures. 2x will be 1x of SSE textures. 0.5x will be 1x of SSE textures.
4x will be 4x of Original Skyrim. 2x will be 2x of Original Skyrim. 1x will be 1x of Original Skyrim.

The improvements will still be great for 2x! Even though this is the same size as SSE, SSE poorly upscales.

Original Skyrim means Skyrim Legendary. HD pack doesn't exists for things in here anyway :-).

Mostly Original textures:
Landscape
Plants


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Is this a flawless masterpiece?
No.


Requirements:
Skyrim Special Edition - wow



Resolution (Current v0.2) - Click spoiler to see comparisons to Skyrim SE.
Also view comparison slider image!
1x:  HALF (0.5x) THE RESOLUTION OF SKYRIM SE. Cleaned textures of Skyrim Legendary, which are actually better than SE, despite being half the size. I use smooth2 model.

2x: SAME (1x) RESOLUTION AS SKYRIM SE. Just doesn't Look like s***. Downsized 4x.

4x: TWICE (2x) THE RESOLUTION OF SKYRIM SE. The 1x, upscaled by 4x using an ESRGAN model.


Landscape: I used manga109 model.

Difference of block compression BC1, BC3, and BC7:
In dds texture (the textures skyrim uses), compression via BC1, and BC3 (with alpha), is blocky. Because of this, in original Skyrim, people sometimes leave textures uncompressed. Uncompressed has a big file size. 
With the new block compression, via BC7, it is nearly the same quality as uncompressed, but has the same size as BC1, and BC3. However, this is only supported in Fallout 4 and Skyrim SE.

For some god-forsaken reason, when releasing SkyrimSE they still compressed the textures to BC1 and BC3. So even If I do not upscale, by removing BC1-BC3 artifacts and compressing as BC7, the quality is improved.

TLDR: Even without upscale, there is big difference. NO MORE BLOCKY! @400% zoom, so you can see the difference.