糖霜is much smaller than 糖.
use糖霜 to make 甜品會令果樣甜品更加軟滑,
desserts like souffle and cookies sometimes use 糖霜 to make it smoother.
It's not so good to 糖 instead of 糖霜.
But if you really want to use 糖 instead of 糖霜,
you need to control the amount of 糖
because 糖 will be sweeter than 糖霜.