green giants can exceed the 8 foot width within 5 years ... depending on size at planting

their height is unlimited .. given enough time

ken

The description sounds like arbs also some could wind up somewhat larger, especially as they attain great age.

for the life of me i have a hard time differenting the varieties brandon and rushmore. hetz wintergreen has a slightly broader growth habit, but they are young they are very much like the others. rate of growth of all three is as fast as you'll find in arbs (t. occidentalis). all have the same primary claim to fame, resistance
to winterburn.

The Nellie Stevens Holly has worked well for us down here for an under 20' screen. Has proved to be fairly drought-resistant also.
Techny Arborvita looks good. We're too hot for it down here, but it should be right for your area. Good luck.