Q.Oleander for privacy screen
I’m looking for a variety of oleander that is cold tolerant (southern zone 7/North zone 8) that will grow 8-10 ft. tall
Calypso, Hardy Pink and Hardy Red are the most cold-tolerant varieties of Oleander however there are no guarantees that any particular variety will definitely grow to the height you're looking for. That said, fully mature Oleander shrubs can grow up to 12 feet tall with the proper placing and care.
These articles may help you:
https://www.gardeningknowhow.com/ornamental/shrubs/oleander/does-cold-affect-oleander.htm
https://www.gardeningknowhow.com/ornamental/shrubs/oleander/pruning-oleander-shrubs.htm
https://www.gardeningknowhow.com/ornamental/shrubs/oleander/oleander-growing-tips.htm