Is it possible to change the Admins OneDrive URL under the O365 securlet configuration after this has been set? Currently I'm unable to do so.
Also, can this URL be any users OneDrive URL within the same tenant or does it have to be same user as the Admin account used to configure the securlet
It is not possible to change the admins OneDrive URL after the configuration has been set. You must deactivate the securlet and reactive with the admins OneDrive URL. To answer your second question, the URL has to be the same user as the admin account used to configure the securlet.