First day is definiely rookie runs and licencing, not sure if the second of a 2 day meet would let you run flat out .
If the wind comes up early it can stop a meet, no wind slows the meet as your waiting for the dust to clear
the course chopps up with use and can limit your traction ,
Grid positions are determined by your passed performance, if your done in the rookie line you will be last in line
May be twice as a guest , need to check that out, as it would allow you to run at a one day for rookie then a later meet to realy try it out .
The whole day rookie thing only started in 2010, before that it was a single pass below 150 i think , then your SCTA/BNI licence limit
You would get more precise answers at Landracing.com
Due to distance i don't get to ElMirage near as often as i would like