Like Optifine, it's a modpack that pre-packages optimization mods for players, but with even better optimization effects than Optifine.
[To be honest, this modpack doesn't include every single optimization mod out there.]
This modpack simply packages high-quality optimization mods, and there's basically no difference in content from regular Minecraft. You can use this modpack as a blueprint to create your own - though I can only guarantee there are no compatibility issues here. If you want to create your own, I can't promise that some mods will satisfy you in terms of compatibility.
In the screenshots captured during the following tests, most graphics quality settings were set to high, and all optimization settings remained at their default values.
Project members
TenkenAmainu
Member