I'm not sure I dare answer a Springs science question; I show a slight but definite tendency to freak her out
There is no type of shield which would repel electromagnetic (laser etc.), kinetic and particle weapons. If you need one, I'm afraid you're going to have to invent it yourself, which has the advantage that you can specify exactly what it needs to do.
A solid, material screen (say a perfectly reflecting superconductor sheet) has the disadvantage that it has inertia, so would take time to put into place. If multilayer, it can reflect back laser beams (and superconductivity dissipates the waste heat at the speed of light), while electric currents circulating in it generate magnetic fields which dissipate particle beams, or plasma (which is by definition ionised). Which leaves us bunging kinetic energy weapons at it (like Roman catapults) or impact fused nuclear rockets. Since we can see these coming, we can try and burn them up with laser weapons; easier for warheads than mere fast moving lumps of rock.
Force fields presumably propagate at the speed of light. We don't actually know, because we can't yet generate them. This makes 'closing the door' much faster. A gravity generator, if one could be built, would make quite a good shield, assuming it could be given a sufficiently high gradient – a sort of black hole a picometre thick. What you would get off it in the way of radiation when it was tuning on or off, and the energies involved, I don't really want to know. And you wouldn't be able to see through it, so you couldn't know when it was safe to turn it off, let alone be able to lob plasma bolts back. A spindizzy lets visible light through, so is useless against lasers and their ilk. A stasis screen allows no time to pass inside the shield, so the on-off switch has to be outside the shield itself, as does the generator, otherwise it can never switch off; which is a pity, as otherwise it would protect against anything, including siege.
A scanning shield (a point shield, like say a quantum black hole moved across the area to be covered like the electron beam in a TV set, although much faster, obviously) a percentage of radiant energy would get through, and, if you synced things perfectly, you could get your plasma bolts out. Unfortunately, if the enemy could analyse your pattern, they could get their plasma bolts in, so perhaps that's not so good an idea.
Or invent your own; nobody can contradict you.
As regards sizes of stellar configurations, Galaxies are big; why not go for a stellar cluster; a hundred or so stars, many probably have planetary systems, a few inhabitable planets or moons (after terraforming; I don't expect to find many use as delivered), plenty of loose junk; radiation levels probably a bit higher than on Earth, but hey, like that you can evolve faster