Hello Wayne,
Different rank settings (e.g. 24bit vs. 16-bit) will certainly significantly affect how much memory an organ needs. Also, different PCs may need somewhat different amounts of RAM to be kept from for their operating systems and other processes, depending on what else is installed on them.
Rank settings (and all other settings) are completely independent between different configurations, so changing one configuration's ranks from 24-bit to 16-bit won't affect the rank settings in any other configuration. You would potentially need to change the rank settings in the other configuration(s) too.