that'd be one of those Try it and see things, test it out , find out, a lot will depend on your computers system, as to being able to handle some of the add on's, and loading up, such as CPU, Video Graphics card, how much RAM you have, and how good all those add on' graphics are gonna take to load up to get the effect you desire, all depends on your computer and O.S. ( Operating System - XP, VISTA , 7 etc) , be sure to read those products as to what operating system they were originally designed under when they were 1st made, some of these add on VFR scenery add on's are getting quite old now, by as much as 5 to 7 years, way before Windows 7 was ever out.  Try it and see , test it out,, bout all you can do, Trail & Error , everybodys system is different and set up different, so others might not have a problem, in some areas with those particular add on's , others, will might have issues - depending on their flight sim and computers operating system.