yes, in GF the planet placement is set, but you can add more than you need and have them spawn at a chance so every time you load that map it is different. Connection chance will also change the phase lane connections.
You can also edit your Map Design in notepad
C:\Users\myfist0\Documents\My Games\Ironclad Games\Sins of a Solar Empire Rebellion\MapDesigner
each star is a ring with the star at 0 and the outer edge at 1 so setting to 0.500000 is mid way, but each HW also gets some starting planets attached which are
you may also want to set the
for these as well