WPMU subdirectories conflicting with domains that share same name.

2 question both of same nature.

1. If I have WP-Multisite subdirectories set up example: tim.mtb1701.com and ginab.mtb1701.com ; then say Joe decides to register actual domains tim.mtb1701.com and ginab.mtb1701.com with a registry; what’s going to happen to my subdirectories.

2. How can I do manual subdomains via c-panel that would read tim.mtb1701.com and not mtb1701.com/tim ?? Thank You Mark Wall