The largest default ac to have a modeled passenger cabin is the Cessna Caravan.
For ac that do have cabins modeled you can use the default 'Eyepoint (move *)=' key commands to move around. They're listed in the...Kneeboard-Keys-View Commands or under Settings>Controls. If you have a spare hat switch you can assign movements to it.
Ac with cabins may also have camera definitions for the cabin area.
There are also a couple of utilities that allow you to use the mouse to move around:
F1View (free) and 'Walk and Follow' (payware-Google to find it.)
As for ac with cabins, I can't help as I fly mostly ga single engine props.
Dave
At that time [1909] the chief engineer was almost always the chief test pilot as well. That had the fortunate result of eliminating poor engineering early in aviation.