So... as it relates to setting a wireless protocol, if I set this parameter to "nv2-nstreme-802.11", does this mean I can have three different stations connected simultaneously using each of the protocols? OR will my bridge only allow one protocol at a time?

Only one protocol at a time.

Does this mean the ap-bridge will stick with whatever protocol the first station associates with?

Yikes, this means a WISP tower would need a radio per protocol.

the highest has priority. if you need mixed nv2, 802.11, etc then yes you will have to have a radio per.

Does the same go for the 802.11x protocols?

In other words: Two CPEs are connecting to the same PtMP sector, if I have one CPE using 802.11ac, can I have another using 802.11n?

Yes, of course

Old post but I'm not sure what that last answer means?

Can one CPE connect at 802.11n and another at 802.11ac both to the same sector?

Yes. If you set it so. But keeping ac and n separately could be more effective.