Radiance ReShade makes highlights brighter, and shadows deeper, without crushing blacks like many other presets do. The sky is the focus of this preset, becoming far more vivid and "bleeding" into the land to unify colours. It also tackles some key issues I had with Skyrim SE, such as TAA blurring the image, and a lack of colour.

Radiance uses:

• Adaptive Sharpening and a Clarity shader to counteract TAA's blurring. Detailed textures will pop again.
• Curves and Tonemapping to adjust the colour balance and contrast.
• Ambient Lighting to bring the skies to life.
• Bloom to boost light sources.
  

Installation:

• Download and install ReShade from this link. Double click the setup file, select your SkyrimSE.exe, and confirm the suggested installation. ReShade will do the rest automagically.
• Download the Radiance ReShade file from this mod. Extract the Radiance.ini file and drag/drop it into the same folder that SkyrimSE.exe is in (not the data folder).
• Start the game, and once in the main menu press Shift+F2 to bring up the ReShade menu. Use the drop down menu at the top to select Radiance.ini (if it's not here, double check you installed it in the correct location, and not the data folder).
• That should be it! You can toggle this ReShade on and off with the Scroll Lock key.
• NEW (optional) step for 1.1 version users: Open your Skyrim.ini file and add "fGlobalContrastBoost=-0.2" under [Display]. This will massively reduce vanilla's black crush lighting issues, and version 1.1 of this ReShade has been rebalanced to these levels.
  

Recommended Mods:

Darker Nights - Radiance takes care of the day time, Darker Nights is a perfect companion for night time. The before/after night image above used Darker Nights Level 3.

Enhanced Lighting - This mod will adjust interior ambient levels to make them darker.

ReShade can't distinguish between interiors and exteriors like ENBs can. The above two mods create darker nights and interiors, so that this preset can focus exclusively on vivid daytime colours. That's why you won't find crazy black crushing and contrast values from Radiance ReShade.

Performance Impact:

On a GTX 970, i7 2600, and 16GB RAM, and ultra settings, I still get 60fps even outside Dragonsreach Palace looking down on Whiterun (a notorious location for low framerates). Your mileage will vary though, as the Clarity and Ambient Lighting components of Radiance ReShade are more intensive than a standard colour filter. Essentially this is more intensive than most ReShades, but still less intensive than the vast majority of ENB configs.

If you want to gain some extra frames, open the ReShade menu in-game with Shift+F2 and disable Clarity by clicking on the box to the left of the shader name. You'll lose a lot of the sharpening and highlighting, but it contributes less to the overall image than Ambient Lighting does. Disabling both is certainly possible, but not recommended given the visual impact. The rest of the shaders are all balanced around these two, so results might look odd.