As far as filament goes - it depends how warm it gets inside the enclosure. You don't want the filamnet to get warm to the point of softening and stretching.
Yeah basically fan facing the room and exhaust facing the window.

Guess you could mount the exhaust on the top, but what I was envisaging was creating a cross current that just removes the air at the top.
If you just have an exhaust fan at the top, then you will draw in air from the bottom of the enclosure that could possibly cool the print bed down.

With a fan blowing in and one sucking out at the top you shouldn't be creating any significant air flow over the print bed itself.

Well that's my theory anyway :-)