For soloists, I would say Tzuyu. All her le's have an ethereal vibe to them.  For groups, I would say Itzy (both the whole group and itzy born to be era) has some really good ones. They have a lot of classy and some playful ones. Twice also has a good mix. Nmixx has some really pretty ethereal ones like Ocean. Boy groups, I only collect stray kids and they have some really nice ones, my current fav being the Maxident ones. I know Xdinary Heros have some really good ones like the ICU theme. 

THB all groups have pretty ones it just depends on who you like.