The device policy is simple. If you add a Corp account to any phone it's subject to device policy, including wipeout after you get fired. It's very obvious when you enroll.
Not so simple, it depends how the MDM/EMM is set-up.
If it's set up to entirely manage the device, then yes it will get fully wiped (we do this for corporate-owned device).
A personal device can access our environment if requested (they have to sign an agreement form, explaining what we can or cannot do) and a work sandbox will be created, in which only the apps installed in this sandbox will have access to corporate data (ex: you'll have a copy of Gmail, Hangouts, Drive, etc in the sandbox).
In the situation of a personal device, a wipe will only remove that sandbox, leaving the personal data untouched.
If it's set up to entirely manage the device, then yes it will get fully wiped (we do this for corporate-owned device).
A personal device can access our environment if requested (they have to sign an agreement form, explaining what we can or cannot do) and a work sandbox will be created, in which only the apps installed in this sandbox will have access to corporate data (ex: you'll have a copy of Gmail, Hangouts, Drive, etc in the sandbox).
In the situation of a personal device, a wipe will only remove that sandbox, leaving the personal data untouched.