Some of Maine's UTs were once organized and they have place names, but at some point they decided to turn in their township charter and stop collecting taxes. They were each at one time 'official' towns and taxed their residents, but now they don't, though most of them are still occupied.
Some of Maine's UTs were never official towns so they are labeled by grid coordinates [like R1 T13, etc]
Since Maine's UTs are not official towns there is very little census data to look at for them. It is difficult to compare them in terms of population, since they do not officially exist. But they are named, they are on maps, and folks do live in them.
List of Townships