Thanks for posting in Q&A forum.
For the first question:
Currently, “Preview” feature based on respective user permission is not available in SharePoint Online.
The only way you can see the site in different roles is to log in as a use in the respective user permission. I suggest you create a test user account in this tenant to see the outcome.
For the second question:
You can adjust what user can see in a list view (see a reference here: SharePoint list views - different permissions for different views), but hiding a column or list properties from certain user roles is not achievable for the time being.
I suggest you share these ideas and suggestions via SharePoint UserVoice so that Microsoft Team can look into it. We appreciate any suggestion to improve SharePoint products.
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