Over a dozen cells means a swarm.
You are doing the right thing by giving them frames of brood and removing empty space.
If you are worried that they may be queenless (more than 4 weeks with no eggs) then make sure there are some eggs on the frames you give them. If it hasn't been that long, and you are just waiting for your new queen to lay again, try to give them frames of "burnt biscuit" - capped brood with toasty brown cappings. These are bees which will emerge in under a week, and best support the population while you figure things out.
Are you currently in the dearth where you are? Ideally you will want to wait to feed until after the goldenrod is done, when they have had the best chance to gather enough for themselves. If they might starve first, you can feed, but feeding in the dearth is dangerous and can trigger robbing. If the hive still has some capped honey, then you can wait a little while. No brood means they don't go through much stores. If they have no capped stores at all, and there is no new nectar coming in, then you may have to feed honey back now.