ALL stacks are possible outside of the Wicked Witch Battle. Best stack I've had was Emerald City + Flipper Frenzy + Haunted Multiball + Munchkin Multiball. BIG POINTS.
I've said this before, but there are so many strategies. Lately I've been playing solely for bonus. Starting Emerald City with either Lights On or Off, then starting either Munchkin Frenzy or Welcome to Munchkinland can rack up a TON of points. For Munchkinland I'll do nothing but hit the ramp over and over with 2-3 balls cycling at all times. In frenzy I go for the pops. Easily 100,000+ for either of those modes with the crystal ball multiplier. Add in the HOADC multipliers for bonus and everything soars. Best bonus has been around 820,000. Still shooting for 1 million.
I've been meaning to get to a strategy video but time has been short. Someday...