The goal of this is to expand the game while keeping a Vanilla feel. The mods listed here achieve this.

Glavius AI makes AIs make better decisions, makes them choose better perks and just be better all around. I find that the AI can actually keep up with players somewhat even on lower difficulties but it's not overwhelming. Additionally making AIs actually choose targets better means wars are more interesting.

Planetary Diversity provides more interesting options for planets and means that terraforming, and also habitability can play a greater role. The special world types are also fascinating and can be similar to
Carrier improvements means that Carriers can actually have roles.

Crysari Vassal means that vassal based gameplay is no longer immensely gimped on higher difficulties. In vanilla, taking a vassal removes all AI based bonuses they have. This makes them very weak compared to how they regularly are.

This modpack also includes a lot of enhancements to crisises. I personally recommend applying the "hard" template to crises.

Just More Empires, More AI personalities, and such provides more enemy empires, and Just More flags supports this while also giving players more to choose from when customising their flags. The same is true of Expanded Colours. The other things like Civics, Name Lists, and the like also enhance player and AI.

More Events, and LEX, and Archaeology Story Pack are excellent flavour that I strongly reccomend.