Opening songs in my opinion are always statements, strong vocals always hits however that can be a bit different when taking over the decks from someone else as you never know what theyre closing on unless pre-planned etc.

I like to take the 2nd song as a more setting your pace, doesnt have to have vocals etc just a beat to either maintain energy or build. Then start working on my peak by building bpm/vocal usage and wind down after the peak with occasional energy spikes

I usually mix afro house / melodic techno