There are a boatload of optimization mods in here, including Rubidium, Oculus, and many of someaddon's mods.

I've also got JEI, Inventory Essentials, Inventory Sorter and some others for an improved client-side experience.

There are tons of mods that update world generation in some way, the biggest ones being Biomes O' Plenty, Structory, Geophilic, and YUNG's mods. There are of course ones that simply add content and other ones that tweak behavior slightly.

Lastly, while I haven't had much chance to test them, I included mods that should make multiplayer more fun, such as Contact, Simple Voice Chat, and Fakenames

The idea here was to have performance optimization, improved vanilla content, and a little extra content on top. Each area of the game should be changed a bit, but not too drastically.

Version 4 Update: I realized I'm moving further away from Vanilla with successive versions. More precisely, my vision for this pack has become less about just improving Vanilla and more about incentivizing exploration as much as possible, without personally feeling to me like a totally different game. In other words, I still will be avoiding any tech mods or any major magic mods, but I may be including mods which add new dimensions or dungeons with wacky content. Once I reach maximum saturation, I may make a new version of this pack that strips the more out there stuff back out.

DISCLAIMER: I have played this pack a fair amount, but I have not tested every single feature. The mods included are all pretty stable and trustworthy, but that isn't to say they might not crash. At the moment, I know of only one issue- this mod does not work on CurseForge with Overwolf. If someone happens to know how to fix this, feel free to let me know, otherwise the issue will likely remain.

FullCraft