If you haven't If you've never played The Witcher III: Wild Hunt, then you're missing out on one of the most celebrated and lauded gaming experiences ever. If you do decide to pick it up though, and you don't have a purist mentality of playing it exactly as it was when it was first released, using the HD Reworked Project Mod is the way to go. It overhauls the entire game's visuals to make it crisper, cleaner, more detailed, and better looking than ever before.
The mod maker, Halk_Hogan_PL, spent hundreds of hours over 5 years and 18 versions to create innumerable 4K textures for the game, created new smoothed meshes to add detail to just about every object you come across, improved the level of detail and draw distance on much of the game's items and models, and created custom shaders and lighting. All of it was done in line with the original style and feel of the game, to make it look more like the jaw dropping experience it was in 2015, but for new and old players in 2020.
Better yet, it does it all for a mere 0-5 FPS impact across the game. You'll need a GPU with at least 4GB of VRAM to play it comfortably at 1080p, but that was the case for the base Witcher III game any way.
If you want to try out the HD Reworked mod, you can download it from the Nexus page, here.