I'm new to DVD..When DVDWS2 writes the .iso file in the finish step, is it in the UDF 1.02 format or ISO, or UDF/ISO?

Next, is it better (in terms of a higher rate of compatibility) to burn the .iso or the DVD folders themselves to the disc? And in Nero, do I need to specify UDF if I'm burning the folders? Basically, on this one, I'm confused as to when you specify UDF, ISO or UDF/ISO...

One more, is there a 2GB limit for the ISO format? I tried to use the ISO/UDF in nero and it says because it's over 2gb, that I have to use UDF....please advise