I apologize for my rude post above, completely unnecessary and frankly mean spirited and has no place in this thread. I've been tinkering with Fallout 4 since it launched and have well over 400 active mods now, I'd hate to discourage others from their own tinkering by being an asshat.
I would highly recommend you stick mostly to 4K textures unless you're planning on spending a lot of time really close to the objects. From a normal distance, like while in-game or for most screenshots you'll never see the difference, and 8K textures will quickly reduce your VRAM to nothing. 4K textures are already pretty taxing in large numbers and if you plan on really going all-out you'll start having issues even loading up the game. I would look at texture optimizing mods before you go too far as well, Bethesda put massive textures on everything from walls to pencils. A pencil does not need a 2K texture, and there are mods that will reduce those to tiny little files giving you more space for important textures like the inhabitants, environments, and major structures.
For a really customizable ENB, I recommend you look at downloading
Natural Atmospheric Commonwealth and use it in conjunction with the
Photorealistic Commonwealth ENB. Between the two there are basically infinite combinations and tunability of the game's visuals. If you're interested, also look into the things you can accomplish making changes to the .ini files. A good example is the game's screen space reflections which only extend a small amount into water and only appear when you are close, but a change to the games files can allow the entire water surface to show SS reflections regardless of distance.
If you go back a few pages and check out my early
Fallout 4 posts you'll get an idea what NAC/PRC is capable of. Self-shadowing, bounce lighting, etc. Just be forewarned, expect massive framerate drops