Paul, as for the Transponder Equipment Code, a little bit about the info displayed on the list. So you will notice the table is separated into two areas, RVSM and No RVSM. This stands for Reduced Vertical Separation Minimum. For pilots flying on VATSIM, all pilots are considered to be RVSM capable/certified. So that leaves us with the second and third columns, Navigation Capability and Transponder Capability. GNSS stands for Global Navigation Satellite System, so basically a GPS. This can be the default MSFS GPS unit or maybe an Flight Management System (FMS). But the reason you see "RNAV, No GNSS" and "GNSS" is because some aircraft navigation systems use an Inertial Reference System to provide location information to the FMS instead of GPS inputs, such as some of the older aircraft (i.e.; B752). So it comes down to knowing your aircraft and what systems are installed. Aircraft who file with a /L or /Z are expected to be able to navigate to RNAV fixes whereas an aircraft with INS (/W) would not. And then, in addition to what equipment is installed in your aircraft, you have to factor in how current the information (AIRAC Data) is in the GPS or FMS to have all the waypoints listed in a given Arrival (STAR) or Departure (SID) procedure. If you don't have a current AIRAC Data set you may not be able to fly a RNAV procedure, in which case you may need to file non-RNAV.
So the basic Equipment Suffix Codes you will file are /L, /Z and /W when flying the heavy metal, and maybe /A or /I if you are in a Cessna 172. Anything in column 3 next to "No Transponder" or "Transponder with no Mode C" will not be used on VATSIM since all pilots are required to squawk Mode C while airborne and when requested by ATC.
I hope this helps but ask more questions if you have them.
