Jim:
You are confused because it is quite complex (at least I found it so).

The vesper is a lovely unit because it has its own gps antenna and AIS antenna (unless you combine via a splitter your VHF...has its own pros/cons). It then puts out its own little wireless signal with GPS and AIS data. Simple to connect an IPAD (an INAVX) then you have a mobile MFD with AIS input, and GPS data (COG, SOG etc). My experience with VESPER has been highly positive..give it 12 volts and it works. Also, again, very responsive to email and helped teach me a lot about interconnecting devices.

Now as soon as you start talking about other instruments they have wired NMEA feeds (at least two different Baud rates and protocols exist). And interfacing multiple brands into a wireless hub can be a fun project or not depending on your interests.

This is a major reason why I went all NKE including their wireless hub (so I actually have two wireless hubs....the weight and electric demand is trivial). I was going to use just the VESPER wireless and that should/could work....but I didn't want to have different companies saying the problem was with the other. I connect to the wireless NKE feed via a tablet computer. Gives me some redundancy.

Oh, and keep in mind most instruments all have some sort of protocol for data transfer that is there own. This is really a thread of its own. I decided after some research to side step the issue and just go with one brand. But again, your interests should dictate your choice...but one can spend lots and lots and lots of time on electronics with no increase in boat speed. A lot of amazing young guys have gone with minimal instruments on Moore 24s and the like very fast to Hawaii.