According to Kranazoli, "ExpandSystemMemoryX64 primary goal is to fix memory fragmentation issues which is very problematic thing in almost all games, fragmented memory reduce amount of really available free memory." Setting this to true can free up some memory for other game processes to use. Of course, setting this to false allows you to change the setting of Sheson's memory patch. If you use the Memory Blocks Log (also by Sheson, great modder this guy) that should tell you exactly how much memory your DefaultHeap is using. If you notice that it is less than the default 512 MB, then Sheson recommends lowering the value in his patch to free up some memory for other game processes (good idea). In order to be able to do this, ExpandSystemMemoryX64 must be set to false. On a personal note, I don't really recommend setting the memory patch value for DefaultHeapInitialAllocMB any higher than 768 as this takes that memory away from other processes. It really is users preference and up to your individual mod list as to what you should do with these values.
Edited by jonny6101, 27 October 2016 - 04:53 PM.