[Gryphin]

RE: Colonizing every planet;
My own take:
Don’t defend planets. Defend Space. If the enemy reaches your planets it means your fleet has been shredded and you are already history.

RE: What to Study
What you study is a “play style” descision.
Colony types: That is a lot of research points early on. If you are expanding fast enough you won’t need the other types till later when you should be able to Trade for or “Acquire through other means” after meeting the right races.
Ship Capture: If you study this early, you may not have to study shields or as many ships sizes, (and several other techs).