basic training: 'bounce' or 'softbox' results in 'diffusion' Period. The amount of diffusion depends upon how you achieve the diffusion. Read on...
Softboxes work simply by taking a relative small light source (flash head) and increasing the surface area that gives off light. Larger always equates to softer. think cloudy sky (soft or absent shadows) vs. sunny sky (hard edged very prominent shadows) Bigger softbox is softer than smaller softbox. Move a big softbox far enough away, and it is effectively a small softbox. Apparent size is what is important. (The sun is huge, but it is small point source in our sky!)
Bouncing does similar thing to softbox, making a relative small light source (flash head) and increasing the surface area that gives off light (big bounce card, or ceiling). Since this typically is much larger area than a softbox on the on-camera flash, ceiling (analogous to cloudy sky) is very much softer than softbox. But if the ceiling is colored, the bounced light is tainted with that color. And if the ceiling is high (or absent, outdoors) you have no surface to serve as a giant diffusion source.
Typically a big bounce card like Lumiquest is larger than a mini softbox but it is smaller than a medium sized studio softbox, so its softness falls in between the two; a ceiling, being huge, is softest ( if it is available for you to use).
The 'tupperware' (Stoffen, Lightspere) both rely upon the ceiling; no ceiling, and you have a useless light accessory that wastes flash power. So take it off outside where it is useless, so you do not waste flash intensity.
Mini softoboxes and Lumiquest are functional even without a ceiling.