Are there gonna be 3 levels now? (Real time battle, planetary overworld, space over-overworld)?

Presumably? There might even be a fourth layer if they go battle/planet/system/interstellar.

Are the space marines gonna march in a phalanx formation?

I doubt it. Round bases man, squares are for fantasy!
But really, I assume they’ll be in a skirmish formation.
Facing is only supposed to matter to vehicles and armour, IIRC.

Which space marine is gonna be the princess?

I am! (Actually I love my 'nids so really I’d be a queen.)