you are refering to sync manipulation of planes in part which is not availible in assy... hopefully that should say not availible YET!!! as I too hope for that ability!!!
I use the plane method of editing extancivy. But I think I'n one of the few who do.
What I do is start out with aseembly planes. I then create assembly driven parts. The sketches for the parts are on the assembly planes, and the sketches them selves are created by projecting other planes. Then end result is stuff that is fully adjusted by the planes.
There are also some costs for working this way.
Cant use family of parts
Must use revision manager to move the group of files together and maintain links
Any object or plane used to control a sketch can never be removed
Many of my Vid's downt show up. I will get youtube when I can. This forum is the only thing I do besides creation of CAD system from scratch.
The service used by the community site for video has acknowledged some difficulties. I will keep you informed when this is corrected.