I was curious if there are any  rules about the music, as this Game Jam is mostly about the Game Boy Aesthetic. So while I understand it will be mostly chip-tune/8-bit or perhaps even 16-bit, is there any restrictions about the rest of the effects? (Reverb and such?)

The only restriction is that it should sound like a gameboy. Your engine may also guide your hand - GBStudio uses the .uge format, for example.

As long as it can convey a gameboy aesthetic there are no hard rules enforced by the jam, but your choices may be influenced by how people vote.