There are solar systems Each star is its own solar system that can have any number of planets. When the map editor is released, you could make 2 solar systems with 100 planets each, or 10 solar systems with 10 each, whatever you like
Solar systems aren't linked together by phase lanes in the same way planets are, though. You can travel from any star to any other star.
There is no galactic travel. It isn't even in the lore. But that doesn't mean it will not be in SINS2. And truthfully I don't see how you could manage that large of an empire with in a real time game.
You can create maps with as many stars or as many planets as you like limited only by what your hardware can handle. Maps have been made with 10,000 stars just to prove it could be done.
If you think of each "solar system" as a galaxy in itself with the sun as its center with each world the only "colonizable" world for a particular solar system like in Master of Orion. Then things fall into perspective. When you zoom all the way out star systems turn into little spiral galaxy's. So that adds to that perspective.