[Suicide Junkie]

For planets, your maximum, (unless you use the same quadrant over and over), varies from game to game but will be the total of all the planets capacities plus any planets you can make. You can control these values in the planet data and the settings files.

Note that you can create more planet space than you realize: given the proper mod files, you can manufacture planets out of nothingness, using a star as a catalyst. (Required object, but not used up in the process)

The memory limitations before RCEs occur are unknown at the moment.