Your doctor would admit you to the hospital for 72 hours to load sotalol. The QT prolongation seen with sotalol occurs in the first 72 hours. If your QT is safe after the drug loading, it is a safe drug.
If you are in sinus rhythm and your atrial fib is not frequent, you could always wait for it come back before you start it. Metoprolol tends to cause less fatigue than atenolol.