No, it is not possible to view what users are currently logged into XProtect.
In case you remove a user on the Management Client, the user cannot log in to Smart Client anymore.
If you remove a user while the user is already logged in on Smart Client, then the user can use Smart Client until it is time to renew token.
This question doesn’t seem like developer question. As it is not related to software development with the MIP SDK, which is the focus of this forum, please ask again in the support community if you need further information on this, you should get better help from the partners using the support community.