This one is an underappreciated gem of a show!
Let me start of by saying I did not watch Kiss, nor did I watch Kiss Me Again.
What I did instead was watch a fan-made cut of Kiss Me Again (edited and linked here on MDL by the lovely Claudeville) which provided me with a solid grasp of all the characters' backgrounds and relationships and was more than sufficient for me to be able to fully appreciate DBKs continuation of the story.
Production quality wise, the series is excellent. The visuals are lovely, the music is fantastic (I am an absolute sucker for dramatic strings, so the intro is right up my alley), and script and performances are incredible.
I've seen some people take issue with the continuity errors between DBK and its predecessors, but personally I think the changes made were for the best.

DBK is still a soap opera, but it focuses heavily on the real issues many queer men have to deal with. The characters' overlapping relationships are complex and there is plenty of drama, but there is a sense of realism and authenticity to the story that is rare in this genre.
One thing the show does particularly well is the way it explores the many difficulties and issues surrounding a coming-out.
It shows the heavy relationship strain of one partner being closeted, the insecurities this can cause to arise, the resentment constant secrecy can breed. It highlights the painfully real social and financial concerns closeted people have to reckon with when they are considering coming out.
Where other shows main concern lies in whether or not their characters can find the courage to openly be themselves, DBK forces its characters to consider whether they even have the luxury to make that choice in the first place. Another user, Moonbyulie, elaborates further on this in their review, which makes for very interesting reading and I highly recommend having a look at that as well should you be interested.

Another strong point of the series are its characters. They are all (deeply) flawed, yet highly likeable individuals whose conflicting backgrounds and ideals lead to many painful clashes and whose individual journeys of character growth are both gut-wrenching and an absolute joy to watch.
They may at times make frustratingly poor choices, but they never stop calling each other out on their problematic behaviour and they never stop supporting and caring for one another.
Even Non, the show's ostensible "villain", is an incredibly complex character who walks the line between hateful and sympathetic perfectly.

In short, I highly recommend giving this show a shot. It's not perfect - some plot points certainly fall a bit short and some writing choices are questionable - but it also offers some of the most compelling and layered characterisations to be found in this genre.
If you enjoy well-written romance dramas that tackle real-world issues with skill and a good dash of humour, then this one is for you.
If you're in the market for a more serious and mature slice-of-life story which provides a well-balanced mix of romance and character study, then you will enjoy this series as well.