Well, it turns out that you can answer almost everything because the DTXMania rip of the track contains the background stem without drums, bass or guitar. At the part we're looking at (0:44) the vocals are doubled up and autotuned, a reverb explosion sound is added, there's a resonant "synth zap" covering the hihat part, a synth arpeggiation comes in, and a delayed pad synth is added to emphasize the chords. It's a lot of stuff but it's not exactly excessive either: each layer is doing something specific. Good arrangement always adds the magic. 2/2