Feijoa may work in 7b, mine have been down to 10 degrees without any damage.

Feijoa are hedged in mild-climate areas. My single bush gets brown leaves after +20-degrees. Next year's fruit will be reduced after +15 degrees. Look for dense young plants with angled branches rather than the more open, sprawly varieties.

I've been growing Camelia sinensis, 'tea plant' in Atlanta(7b) for 4 years. They've made it through the winter unprotected. They are slow growing but would make a beautiful hedge. I've seen rabbiteye blueberries trimmed as a loose hedge. They are mostly deciduous, but somewhat hold on to their leaves, slow growing, and the birds will always win. I don't know anything about 'goumi berries', but they are related to the eleagnus species that is grown along the interstate. I don't know if they are invasive or not. I would check. maybe hazlenut, it is deciduous but it might make a cool tree hedge. Or a Belgian fence, a type of apple tree espalier. Since I'm 'off the tracks' you could also do a low double wire muscadine fence - deciduous, but a green wall all summer. Apples are hard, but muscadine and blueberries are bomb proof. Needless to say, I wish I had a long length of sun.