Lighting is probably the most underestimated tasks of game art while being one of the hardest to master.
If you're starting out don't worry about mistakes or "doing it right". Experiment and have fun at worst you'll learn a lot in the process.
As far as overlaps, I don't think it matters only that you might end up with some lit areas getting "blown out" (too bright). In which case can adjust your light settings.
The only technical advice I'd offer is to make sure to use a lightmass importance volume
in order to keep your "build lighting" times to a minimum so you can go through more iterations in less time.
Oh one other thing, be sure to make proper lightmap UV unwraps
for your static meshes. It will make a big difference in the quality of your baked lighting.