Wow, I don't know if others had this feeling but I really thought these were so so similar. The main thing is the aesthetic, it has this beautiful environment with memorable side-characters in each. Also, one focuses on poems and one on calligraphy, so they ended up have similarities in having calming words and important sayings as a theme used throughout.
A second thing is the personality of the main leads. They both have a love triangle and meet in work. In the love triangle there is one overly rude character, though in A Poem a Day it's the SML and in More Than Friends it is the ML. Also, the female lead's personalities are so so exact copies, I personally love it and they are both really great and not too weak characters. The drunk FL scenes are both hilarious and crazy. Lastly, a similarity is that the FL ends up liking the ML first.

It is helpful if you press the "Voice Actor" Tag, this is another cdrama that has a similar premise. The FL's profession has to do with voice acting and the couple connects through related work.

Love O2O is also game themed and Yang Yang the ML actor is the same as well. It is a cute campus drama and is pretty popular.