The biggest thing I had to learn about indoor flying, was simply to reduce throttle and keep the plane JUST above stall speed.
Outdoors, speed is usually a good thing, indoors it makes thins happen WAY too fast.
The really light indoor 3D planes fly at a fast walk, maybe 5-8 mph.
Good luck, the ceiling in my indoor flying area, averages 14'
You could build almost any plane with open stick construction, and cover it with ultra light material, some people have used the slightly sticky and lightly colored, covering for leftover food bowls, Saran wrap
is a sourse of almost 6000 plans for model airplanes. They have every type of plane. and you can download them for free. You should be able to find a decent plane there.