Hello,
I believe your setting is appropriate for the newer OS than what is listed in our documentation. With our newer feature of using the desktop count, we no longer recommend you change the SharedSection value unless absolutely necessary to get the number of sessions you need. With only 200 sessions you should not need to alter the SharedSection value.
I believe 4 GB will handle your setup without issue. Each ssh session will take approximately 5-10 MB of RAM.
For 200 sessions, you will most likely need to increase your desktop count. Please run a load first so that you do not unnecessarily take resources from the system. Each desktop you configure will be created and if the resource is not needed, your system will perform better with it available to other resources.
If you cannot get the 200 sessions you need, slowly increment the Desktop Count in increments of 4, until you can get the sessions you need.