So a pan-Orthodox council doesn't necessarily include all autocephalous Churches
Yes, it generally indicates that all autocephalous Churches had representation present.
and doesn't necessarily have any universal authority or binding?
Technically, the only reasons why Ecumenical councils were binding were: a) the Emperor usually codified the decisions into the Civil Law Code, and b) most Bishops were generally there anyway, rendering any necessity for individual synodal votes moot.
So that would mean a pan-Orthodox council is nothing like an ecumenical council--am I correct?
The Pan-Orthodox synods have been a lot like the Ecumenical Councils, minus the extremely and popularly contentious heresies (generally), the sheer volume of hierarchs, and the support/legislation of an Emperor.