As always great advice from Jude DaSheill:
In Emacs you can set the auto-save-interval SETQ to whatever you want; suggest you increase that number of interval of keystrokes required before an auto-save or maybe just turn off auto-saving altogether--if things start to slow down
If you do try Linux; and everyone should at one point, realize that in Linux you can easily create & mount extra "swap partitions" on your hard drive which can be used in lieu of memory and/or in addition to it, if indeed as you wondered, there may be a bottleneck of memory usage when you try to use OrgMode--adding swap space may help--maybe not, I haven't looked into it recently, don't want to get your hopes up for such a solution
In Linux you can also use exotic things like PVM--Parrallel Virtual Memory--i.e. use memory from OTHER machines YMMV
In Linux you can also use Emacs OrgMode and/or VLFMode i.e. "Very Large File Mode" and/or use FUSE to meld directory trees together with remote machines & then edit with your best machine, the machine with the largest RAM--with VLFMode in Emacs you can edit files of ANY size (since it only puts in part of the file at a time)--or you could try VLFMode in the first place; please tell me the results if you try that--does it speed up things for you? Does it solve your problem?
Strongly suggest splitting up large OrgMode files when things slow down and/or just putting a link to those other files that you may want to use when in your main OrgMode file by using the file protocol:
[[file:~/my-OrgMode-file2][File2]] [[file:~/my-OrgMode-file3][File3]] ...
Other than that, I'd suggest trying to use CygWin on Windows first if you haven't used CygWin yet, CygWin comes with XWindows & many other things related to Linux that you may be familiar with can be used too--CygWin was donated to the Free Software Communities from Red Hat--many thanks Red Hat!
What do Kill Gates' Micro$loth WindBlows users use now to run Emacs & OrgMode?--y'all use CygWin right?
Installing CygWin on Windows is quick and easy & then so is installing Emacs and/or OrgMode after that