Tupperware just helps difuse the light so its not so hot and more even.
Ilya honestly I’d always keep the flash on the camera, when shooting weddings etc it looks much better when theres even lighting throughout the shoot. Plus eliminates the need for a tripod at all.
While some are against flash if not need be it allows for a more uniform look.
Just my 2 cents from shadowing my uncle, hes been shooting weddings for 30+ years