In the first two maps it seems like the other player has a small force (2 or 3 frigates) at all nodes adjacent to mine right from the start.
If you look closely, you'll notice those are cleverly labeled "local militia" -- they have nothing to do with your opponent, they're just the local forces of the planet, defending it from foreign invaders. Like you

(Or your opponent)
If technology was available in real life like that you probably wouldn't even go any where near the sun.
What, phase lanes that connect from planet to planet, with only stars going to other stars? You bet your buttocks we'd go to the star if thats what it took for interstellar travel!
However, I found it really makes a battle easier if you just select all of your units and have them all fire on a single enemy capital ship, one at a time, until they are all gone.
Personally I prefer if you FF on enemy
frigates first, then take out capitols after they're without their friendly unit support. Its all a matter of opinion. And unit AI
is going to get improved, come the beta that actually is interested in gameplay.
and there isn't any sort of penalty for it (like damage from friendly fire or something)
Shield mitigation is supposed to discourage this approach -- the more damage you do to a single target, the less damage is actually done for as long as its shields are up. The "Shield mitigation" factor is the % by which damage is reduced before being applied to shields.