Optifine is now available in a stable release for version 1.16.4 since today. If you enjoy shaders and also want to optimize Minecraft, i recommend you to install it. It is very easy, you just need to download the right version then launch it and in a few seconds you will have it installed.
Shaders in Optifine
In june, i did a post about my top 3 shaders for 1.15.2. I still use those 3 and this post is still a good reference if you want to start enjoying Minecraft with some of the best shaders available. Just to give you a few examples, here are 2 screenshots of the “almost ready” Waterlands free server, without and with shaders. I use the last BSL version mainly. Enjoy !