WTB Softboxes/Beauty Dishes
all the items you mention are not "one brand(modifier) fits all/any other brand(light source)".
as with lens mounts and camera bodies...
you'll need the proper mount(adapter) for the light modifiers to fit your light(s).
i spent hours and hours and hours 'researching' and went with Alien Bees (Paul C Buff).
PCB is good affordable made in USA equipment. plenty of selection/accessories, great service, and again...good equipment.
i wouldn't fall on a sword to claim it's the best but its good and more than plenty good enough than i need.