How would other vatsim members aircraft appear on say my screen.also would they use high quality payware/freeware aircraft?(e.g.nippon cargo b747)

If you're using FSInn, it will have some intelligence of how to map other user's aircrafts.

 

This is based on what ICAO Aircraft ID they've put in their flight plan. 

 

You can also specify yourself what aircraft you want to see for a particular user.

 

In the options you can specify to use 'lo-res' models of aircraft.