Like Genesis Plus GX, there is an option that lets you set how wide the screen will look on the TV output, for 4:3 this is currently 672 which is pretty neutral but could be set to something much higher on some TV sets to fill up the screen.

Additionally videos that use square pixels are not displayed correctly with 672 and should be 704, a good live example is the Netflix Wii app that is probably using the same value and you can tell by calling the HOME menu and seeing the position of the images which should be either very close to the edge of the screen or already dipping from the safe area because of overscan.

Depending if you either want to see square pixels or just fit your TV the sweet spot will always depend on your TV, that’s why an option to specify is useful.

If someone can compile a version that doesn’t use the current values, I could hex compare the binaries and figure out where the value is stored and edit it anytime I want completely manually.

For 16:9 this value is 720(max value) and 686 for NTSC and PAL respectively. The lowest value is 640 and was often used as the default for many GameCube and early Wii games.

The values go from 640 to 642 to 644, etc up to 720