I've never been very fond of Superpower, I've always prefered SubPunch. Anyways, I'll leave that decision to you, as you already have perfect neutral coverage.
Sigilyph is boring :/ You should run Kerech's Sigilyph, which I do believe uses Stored Power / Roost / Charge Beam / Cosmic Power. Can't quite remeber the Spread, hahaha.
Considering this is BW2, Galvantula does get Giga Drain, which allows you to heal yourself for 5 less BP.
I'm feelin' electric tonight
Cruising down the coast goin' 'bout 99
Got my bad baby by my heavenly side
I know if I go, I'll die happy tonight