Question says it all
Replay
Nope. I didn't use Gengar, but the effect would be the same either way.
Hope this helps! :)
NO, it doesn't trigger weakness policy https://replay.pokemonshowdown.com/gen8doublesou-1195576752 aegislash was holding a weakness policy, Night shade does a fixed amount of damage, and therefore doesn't count as super-effective. Same with Dragon Rage and other fixed damage moves.