So I've been thinking, every 757 has a sort of detailed cabin with opening bathroom doors and everything. But for some reason the plane is laggy and I lack fps everywhere I go, despite having the requirements to run the add-on. Does removing the cabin and the opening door functions on the CS 757 increase FPS and make flights smoother?

Thanks

You can try yourself, simply a click in ACE.
For my experience, didn't make much different.
Also in ACE you can change the resolution and refresh rate for EFIS, that could make quite some difference in performance, you should try it if it's laggy.

BTW the non-cabined cockpit is been upgraded with some more detail in cockpit, that's great for using, but might be a little heavy on performance.

I just tried removing it and it doesn't seem to make much of a difference. Anytime I am operating out of newer addon airports my fps is less than 30. It just happens to be a very performance heavy aircraft.