Featured servers uses their own softwares. Lifeboat uses a fork of the old Pocketmine. If you are going to make some kind of survival or creative server I recommend Nukkit because it has more features implemented. For a minigame server you need to check if there is the minigames you need available or are you ready to hire a developer to make them for you. There is probably more free minigame plugins for Pocketmine.
they use their own software, then, is there any place that i can go that would be good for learning to make my own software, like how the Hive has its own custom software, or cubecraft uses a modified bedrock version of Spigot and bungecoord?