Looking for expanded documentation on Exchange objects

Here's the whole Exchange powershell module documentation. From this link you can basically navigate to any parameter and any property with explanation - https://learn.microsoft.com/en-us/exchange/client-developer/management/exchange-management-shell-cmdlet-input-and-output-types

For example your requested documentation about mailbox properties that were found through the URL above https://learn.microsoft.com/en-us/previous-versions/office/exchange-server-api/ff328629(v=exchg.150)