Welcome from Castle Rock. No experience with top bars, but I imagine the bees will sort it out. With these early flows, they should be making comb immediately. You might consider providing them a restricted feeder - slow & steady, in case the flow becomes intermittent. If they are calm (as you say), and you see them clinging to each other when you spread the frames, the queen is probably in there. Give them a week or so to get the ball rolling, then check for eggs/brood.