The easiest way to use a variation in SQL engines is to make a new DB-API database. You can do that by changing the default backend in Preferences -> Family Tree -> Database backend, Converting an existing database (new button in Manager), or CLI importing:
behavior. database-backend:dbapi -C "DB-API" --import filename
Once you have a database, you can edit the default_settings.py file in your grampsdb/*/ directory.