Hi Kent,
Oxygen currently uses the heap indirectly via oleStrings. I don't know how the heap used in the current process relates to the space used by other processes. It's a black box to me. You can use shared memory blocks, shareable with other processes, however. (Like sharing a file, but in memory.)
The stack should be the fastest memory available, since it sits in the CPU cache, but this is also a black-box area.
In addition to heap space, code space, and stack space there is also the pre-allocated program work space. This is for globals, statics, import/export tables, and various other sections loaded from a binary file.