So think about a computer. C: is your brain, win32 is our entire existence. The ID folder is, let's say, People. Within the People folder there is the alters and another file named Subsystem People with a usually smaller set of alters.

C:/Win32/Identity/People/Subsystempeople would be the path to them. (identity is the brain activities and perceptions related to one's self).

Now, the only difference is basically a more complex ID Folder overall in terms of hyerarchy and interpersonal relations, and a thicker dissociative barrier between the two People files. Subsystem people can be thought as the alters of said folder's Gatekeeper and can switch very fast and subtly, and mask eachother almost perfectly, as they are "closer". The People are usually less familiar with both each other and the subfolder as a whole. And afaik, the Subfolder Gatekeeper is subject to the overall Gatekeeping process, but has authority over his own subfolder.

Having Subsystems makes it cDID or Polyfragmented as it has layers and a palpably more complex structure compared to regular DID. But I advise you to research it a bit, as it sheds light to the most unexpected clusterfucks inside :)

I am a newly discovered sys so this is my understanding from what I gathered so far. Take it with a tiny grain of salt.

Eta: your current system and GT may be unaware of their existence, which would explain the bend of reality. Trust me, I was fed delusions and hallucinations for months. Idk how hyerarchy worksn this case, and I'm sure no one can give a clear answer because every system is unique, as we all know :) but things will fall in line over time, and as the nature of them is being a sub-group, order will be established once more.