I'm searching for a light hearted dramas with strong messages, or just a light hearted dramas. Basically, not too much actions, but there is still something going on.
Some I've already watched are : 

Age Of Youth

Age Of Youth 2

Because This Is My First Life

Cheese In The Trap

Hit The Top

Shopping King Louis: this one is lighthearted to the extreme, so just focus on the fluffy haha

Sassy Go Go: This one is short and light, but also teaches about friendship, teamwork and has soome focus on studying too.

Love O2O: This one is chinese, and a bit longer than your usual kdrama. Also is cute.

(Only if you're into BL) Make It Right: The Series and Two Moons are good picks

Boss & Me: Another lighthearted chinese drama

Reply 1997: Actually all the Reply's series can count, althought I don't really know if the others are as light since I only watched this one.

Considering your list, I'd say you watch Sassy Go Go or Reply 1997, they focus more on a group of friends rather than one couple, althought the main couples are still well stablished. 

Those are light hearted yes, not so sure about strong message though lol

Cunning Single Lady 

My Secret Romance

Noble, My Love

Something about 1%

Go Ho's Starry Night

Those are about 80%-85% light hearted and have a message

Fight For My Way 

School 2017

High School King of Savvy

  • Weightlifting Fairy Kim Bok Joo (probably the closest to what you're looking for)
  • Coffee Prince (older, but a classic) 
  • Attention, Love! (Taiwanese)
  • Splash Splash LOVE (a drama special / short)
  • Ugly Duckling Series: Perfect Match (Lakorn / subbed on youtube / short)

I second the notion on Weightlifting Fairy.   And I'll add 

  • You Who Came fr the Stars and
  •  Legends of the Blue Sea.

Reply 1988

Avengers Social Club

The Lover tells about everyday life of couples who live in the same apartment but have their own issues.

The Sound of Your Heart is a webdrama with lots of comedy - you could try one episode (they're not that long) at first , that should be anough to hook you up with this drama :D