Fairplay:
Are the plots of these pretty solid? or it's more on gags & plot is just secondary?
The three of them have pretty solid plots, with some elements of comedy.
Rooftop Prince has quite a lot of comedy in comparison in some of the earlier episodes, but the comedy is balanced out with serious plot points too. Most of the comedy arises because the main male lead time travels from Joseon era to modern day and is therefore not used to modern technology/culture/conventions, etc...
Healer and Chicago Typewriter have more serious tones to them overall, in particular with the historical storylines involved with each of the dramas and the mystery connecting the past to the modern day.
Chicago Typewriter has less nuances of romance, although there are some romantic scenes between the main couple, and is more overall friendship-focused, with some endearing/funny scenes.
Healer has a really sweet romance that happens alongside an overall serious plot, with some comedic scenes and elements to it. I'd elaborate more on the comedy aspects of the latter two dramas but it'd (potentially) be spoilery.