Before installing the mods, a few thing need to be installed
1 - If you haven't already, sign up at the Nexus. (LINK) It's free, and it takes 2 minutes.
2 - Download and install the NexusModManager (NMM) (LINK) *Install descriptions are found at the Nexus page if needed.
Download and install
Extender" (SKSE). (LINK)
You can either download SKSE as a .7z package or as an installer. If you choose
the package, unpack the files to the root of the Skyrim game folder. If asked, overwrite any other file(s).
Make a shortcut on the desktop to "skse_loader.exe". This should be
used to launch Skyrim from now on.
If you have the Steam version of Skyrim, then download SKSE from Steam instead. SKSE is free on Steam as well.
4 - Download and install TES5Edit. (LINK) It comes in a .7z package. You can unpack the files to where ever you like. The program will ask for paths once executed.
5 - Download "SKYRIM Save Cleaner". (LINK)
Download the latest main-file manually and unzip to where ever you like.
*You need to be signed in to the Nexus to be able to download the file
6 - Find out how much video memory you have on your graphics card. If you are not sure, use this tool made by Boris Vorontsov. (LINK)
7 - Make some coffee. Downloading and installing all the mods will take several hours, so be prepared. However, at the end you will get the result from several months of tweaking and testing.
Curious if the results are worth the effort? - Here are some before/after screenshots.
*To make "before" screenshots, I would have had to uninstall every single mods again, so I found some screenshots using Google and Bethesda's Skyrim site instead. I then took some as-similar-as-possible screenshot with SBP ENB settings enabled and all mods loaded.
ENB 3.08 Screenshots
ENB 2.54 Screenshots