I am planning on doing a stream of galaga (which might turn into a speedrun if I see that I can do it). What are the exact default settings so I know how to setup my gameplay? Just asking so I don't face a possible rejection.

If you run an official copy of the game whether be a port, or a legitimate arcade rom, these settings are typically the ones that are fresh when you start, and does not involve messing with any dip switches or settings in the in game menus.

The default settings are

Lives: Start with 3, get one for 20k points, one for 70k points, then everyone after is 70k points

Difficulty: Hardest If I recall correctly some Namco Arcade Ports sometimes don't point this out as hardest, but an easy way to check this is, if after round 1, and every round after enemies fire at you as they come in for formation. So I'd suggest playing rounds 1-3 and paying attention to what it is, if not change it till you get to the correct one.

These settings are essentially the "fresh out of the box" rules for Galaga and these are the important ones that are checked for verifying runs.