Do I still have to live in a regional area after I get the subclass 191?

The regional condition (such as living and working in a designated regional area) applies while you hold the provisional 491 or 494. The whole point of the 191 is to release you from that restriction.

After the 191 is granted you can move anywhere in Australia and take any lawful work. That said, you must still have genuinely met the regional living, working and income requirements during your provisional visa years to qualify for the 191 in the first place.