Users with multiple devices using Hotspot

Hi all,

In my organisation, users have more than one device.
When logging on through the RouterOS Hotspot, they can enter their username/password. Works fine. I even see the same user appear multiple times in the list of Active users (when he/she is using more tha one device)

Now, I would like to help my users when it comes to smartphones.
I was thinking of pre-registering the MAC addresses of these smartphones, and allow MAC login.

Is that possible?
Can a single user combine multiple authentication methods (one of which is MAC auth)?
Can I count all traffic of that single user account, across the different auth methods?
Or will I have to create multiple user accounts for a single user? (One for each auth method.)

Thank you!
J.