Agreed about the easement.
I see a utility pole in one of your pics. That and I'm willing to bet the neighbors fence stops at the easement line.
So I would either find the easement and build a wall back towards the easement line and grade to the street.
If you don't do a wall, then you could do boulders or some sort of larger stone garden with a fence on the high side. Then slope back at the easement line and landscape to the curb with generic perennials that can either be dug up easily or destroyed without any issues.