I have plastic "Seitz" windows, some are top hung and some slide. Both are proud of the body by maybe an inch, and there are quite a few scratches. I've since put some spare 3M clear paint protection film on some, and some left over office window mirrored tint on another which may help prevent more damage in the future, but may just get ripped off by a big overhanging branch! The relective film coating hugely reduces the heat coming in from the sun though, handy when its hot, not so good when its cold and you want all the heating you can get!
They are double glazed as far as that sort of thing goes, there's an air gap in the middle that gets smaller towards the edge. When its really cold some trimmed to size foam camping mat between the window and the "thermal" blind helped a lot!
The mozzie net/ blinds are good, keep out most insects and just about all the light, both from inside while covert camping, and from outside in brightly lit carparks.
A dutch camper on a truck I saw had steel grills welded over all his windows, which, if you can still get out if you had to is good, if you are going on tree lined tracks slightly narrower than your vehicle.
Top hung windows are good for ventilation when its raining though!