@FlowLive I guess the only question I am seeing is that you are asking how to determine if the machine is a laptop or desktop. The easiest way to accomplish this is to use a script as the snap in that will check if it is a laptop and if so run the installer from a share some where. If it is a desktop then no installer is run.
Natively there is no way to have FOG determine if the machine is a laptop. But if you know what machines are laptops as you add them, you can have machines belong to multiple groups, add all laptops to a Laptop group and apply only those 3 snapins with no other setting in that particular group. Not automatic, but does work.
I quite often use scripts instead of actual files for snap ins, mostly due to old limitations of snapins back in the .32 days, so I guess it is just an old habit.