realizing we definitely have some complex impostor syndrome thoughts with regards to our own plurality
We do too, but mostly Logan who is our "original"... he fears that he's controlling all of us just because he feels like he can see everything happening and how everything works, and being able to see that makes him think that he is doing it.
The rest of us don't feel that way because we're all confident in our own existences, due to the fact that we have our own individual self-identities and personalities... but Logan, knowing he is an "original", feels that he would be the one controlling everything if we were faking. So he is the one who gets the majority of the impostor syndrome.
Accepting that you're in a system requires you to accept the fact that you will feel things that directly contradict that fact. You will feel like you are a singlet and just imagining or acting. You will feel like you are the sole inhabitant of the body.
At the very least... try to keep willingly identifying as a system despite the fact that your brain keeps trying to make you feel otherwise. The next step is to learn to doubt the accuracy of those feelings... but for some, that's not possible (like with us), so the most we can do is try to ignore them.
Ignoring them won't necessarily help with the impostor syndrome, unless you can somehow become comfortable with it or keep it off your mind...
For us, we have all sorts of theories on all the different ways that we could be a system, and we personally hold the opinion that it doesn't even really matter how our system works if we feel plural and act plural. We just are plural and fit all the criteria for DID, objectively.