For limiting concurrent sessions you could use
Auth::logoutOtherDevices($password);
https://laravel.com/docs/5.7/authentication#invalidating-sessions-on-other-devices
If you call this function it invalidates all other sessions so you could limit users to one concurrent login.
Why do you want to use separate session tables for user and admin ? This isn't supported out of the box so your most likely going to write a custom session driver.
https://laravel.com/docs/5.7/session#adding-custom-session-drivers
It's an unusual requirement so if you can explain in more detail we might identify a better solution.