Mood sampler meaning? Kpop idols who does it?

I have no idea. I've only seem SM doing it. Wendy, Baekhyun, SHINee, Irene&Seulgi.

I have no idea but it gives feel good vibes so i like it

It’s kind of like an intro to the concept the artist is putting out.

I think it is just an SM thing. Yes, it can be a little better than the teasers. I personally don't watch most of them. I've only watched Kai, SHINee, and Wendy's. Usually, I'll just wait until the album snippets BKA "medley" vid is dropped. That's pretty much the vibe sampler for me.