It was raining cats and dogs. (instead, describe a powerful rainstorm)
A metaphor:

The rain was coming down like a waterfall.

Explanation:

A metaphor uses like or as.

'It was raing cats and dogs' is an idiom

there is 2 main differences, basically which are the users and the market. the other difference is the kind of content

people who use tik tok are mainly people from east asia, kind of like the app douyin. musically, on the other hand, are used by people from america or european countries.

while tik tok videos show things like daily life videos, comedy, or just funny videos, musically are like people mimicking songs with their own actions, 'imitate' singers and video clips.

hope this !

you didn't show the passage, so unfortunately i cant you.