I either sit on the tubes or on a seat slid all the way back, depending on what else is in the packraft and how it all fits. Solo in the 2-Person, I use a kayak paddle – the longest one I have. If I was paddling with another adult, I might choose canoe paddles because it’s less annoying (you don’t smack paddles if the person in the rear stops paying attention). I’ve done a lot of canoeing and kayaking, so both paddle types feel natural to me, but you might prefer one or the other. Solo, a kayak paddle will be more efficient.
As a point of comparison, the 2-Person packraft with weight in it handles more like a canoe or a double sea kayak (i.e. not very manoeuvrable), while the single-person packrafts handle more like river kayaks (you can turn on a dime).