I wanted something cheaper than Hepco Becker and i tried the soft bags for a while. When I found them inadequate I simply u-bolted Pelican 1430 cases onto the soft bag rails from Triumph.
Those Pelicans are the ones that open from the top, not the briefcase styled ones. Waterproof lockable and not at all fancy they cost $65 each. They hold enough, with my topcase for a weeks worth of mountain riding, don't stick out too far and I can remove them and the rails together simply by unbolting the rails, two nuts each side...
The top case is an Emgo, at $90 more spacious than it looks
and impossible to lock your keys inside.