I typically have my seat so high there's not much difference between standing and seated. Maybe a couple inches. Gotta get that near full extension.
Superfluous movement is just wasting energy. Like swaying back and forth.
I'm kind of doubtful how much your arms would aid you beyond stabilization. Minimally, I would imagine lifting your other leg would be much more effective at increasing power transfer. Especially if you're clipped in....
Indeed, pedal the bike, cadence is key. And I just don't really see you arms really helping at cadence speed. Maybe if you're like gruelingly pushing at a very low cadence?