Both shows revolve around mental health. They have main and side characters with traumas and/or psychological disorders but are able to show their identity beyond them, as whole persons that may have a disorder but are not defined by it.
Although both shows have drama as well as comedy, It's Okay That's Love has more comedic moments and more levity to it, while It's Okay to Not Be Okay is a more serious show with more melodrama and a hint of horror on it.

Both dramas are about the Japanese occupation period.

If you loved the story of the past in Chicago Typewriter and wished they had a drama just for them, then you will love Gaksital. The Bridal Mask is more serious and (even more) tragic, but also has the epicness and action that Chicago Typewriter lacks.

It also features a love triangle and a heroine that loves the unknown man that saved her in the past.

The Bridal Mask also features an epic bromance, but it is bleaker than the friendship in Chicago Typewriter and infinitely more complicated.