Hi @SathishkumarSingh-4967
As per your concern about the Cached mode and Online mode, basically Cached Exchange Mode is the preferred (and default) configuration in Outlook client. It no longer depends on continuous network connectivity and most users find it works faster than Online mode.
However, considering the fact that the larger the data file, the more application pauses or performance issues you may experience, agree with Andy that it's recommended to keep running the primary account in Cached mode, and meanwhile, disabling the caching of all shared folders by Clearing the checkbox of "Download shared folders".
Here's an official document about Cached Exchange Mode and Online Mode for your reference:
Plan and configure Cached Exchange Mode in Outlook 2016 for Windows
Regarding the limit of 32 sessions, please refer to the suggestions provided by Andy to disable the auto-mapping. Furthermore, you may consider creating some public folders instead for shared access to information within your organizations. See Public folders.
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