I think it helps that I do lampwork myself, and that I have seen both the stone ones in Idar Oberstein, as well as the glass ones in the Czech Republic. One thing that can be a distinguishing mark is if the bands are not completely parallel. When cut from banded agate, usually the bands are parallel. They may be on an angle, buu then all the bands are at the same angle. In your glass beads you can see that the black 'bands' do not really run parallel.
And like you say, often there is a tail of glass or some overlapping.