If you are placing your storage/display shelves below the layout, I highly recommend plexiglass doors. 2 reasons: The area just above the floor is the dirtiest in the room, which will then get all over your nice clean trains, and 2 plexi will keep errant shoes and toddlers from whacking your trains. Meanwhile, you can still see them. I'd skip the GG track and go with grooves cut with a table saw to accommodate the flanges.
My 2 cents.
Chris
LVHR