Mega worlds are best because of their admin sprawl efficiency (fewer planets, more pops per district), so relocate your empire in the later game to ringworlds to reduce sprawl

Habitats are your best resource for multiplying space-base strategic resources AND making dedicated refinery worlds. Strategic resources are far more powerful- and worth fighting over- to get this district efficiency. Building upgrades are district-efficient Do you build 3 urban districts for 3 science labs- 0.3% tech cost increase- or one urban district for a a tier-3 science lab for the same number of pops who don't have to overcome the. The one you will have the biggest effect on is the district arrangement.

And of these, three of them- planets, systems, and pops- are relatively static. What these mean is that while wider is better- you can brute force the science and unity cost with more pops- sprawl efficiency is key. In the current balance, every 10 admin sprawl is a 2% science cost and 4% tradition cost increase. In the 3.3 beta, we are looking at a district efficiency meta. The quality of your first 40 pops is more important than how fast you grow your next 10, and such. In Stellaris 3.1, there is a pop-efficiency meta, in that while more pops is better, how efficient those pops are matters most. Conquest was good less for the pops it game you, and more for the fact you could grow more pops on more places. In Stellaris 2.7, there was a pop-growth meta in that growing more pops as fast as you could was almost always the best thing.

Science-rush is a glass canon Diplomacy is King.

The early game is going to get a lot longer.

Obvious it's a beta, things are subject to change, I won't focus on some of the obvious balance issues to be addressed (like Edict cost scaling or Machine sprawl penalties or how busted Nihilistic Acquisition is at this point). This is based on a few hours of testing the early game with a few different builds. This is not a total review, but some thoughts and reflections on what the current beta suggests 3.3.

How to play stellaris beta