The Original Smith is the one that started it all off and disobeyed. If this is the one that fights Neo at the end is unknown and would be almost impossible to prove/disprovce as there are so many. At best the one Neo is fighting is the one that that took over the Oracle but again, we don't know and it can't be proven/disproven.
Do they all share the same mind? I'd like to think so as they all seem to be in on whatever one Smith is trying to do. If not that would require them to have planed it all out in advance and that would be quiet a feet with that many Smiths.
Real world Smith I would think had no comunication into the Matrix Smiths outside of jacking in again. Bane though has little to no screen time of his own so we don't know what he did other then screw over all those ships, kill Maggie, and sneak onto the Logos. But you can take the idea that Smith is Neo's opposite and that since Neo had a direct link to the source that Smith may have had a link to the Matrix.