I'm struggling with the landscaping at our new home. The house is high on a hill with gorgeous natural woods in the front of the lot and the back (we're in the foothills of the Smoky Mountains).

Where our land starts at the top of the hill (back of house) there is a large landscaped hill, then grass, then the house, then the front landscaping/grass, another landscaped hill, another terrace of grass, and the front woods (see pic for an overview).

The bones are good, but the previous owners carved out these two hillsides and a) didn't plant much and b) didn't create barriers between them and the grass. The last year of our living here it's been a constant battle between me and the grass and weeds that creep onto the hillsides.

So I'm dealing with it one way by planting the hillsides with plants that will fill out the space and prevent erosion. But I still don't know what to do about the edging. I've read and read and can't figure out if I should be doing

1. A simple edge cut out and kept up
2. A plastic barrier-type edging, possibly topped with a line of natural stones
3. ????

I would appreciate any and all advice or experience. Thanks!