We've used SourceGuardian encoder in the PHP 8 version of the myDBR. This is due to fact that it has taken longer than expected for ionCube to produce the PHP 8 version of their encoder. Once ionCube does release version 11 of their encoder (compatible with PHP 8), there will also be an ionCube encoded version of myDBR.
Both ionCube and SourceGuardian work the same way and there is no difference in which one to use. Loaders for ionCube can be found here and loaders for SourceGardian can be found here. myDBR will help you choose and install the loader when you run the installer.