-Supportive, healthy relationships in both.
-ML's are highly intelligent
-FL's are very passionate in what they do.
-They both involve the leads living together in some way.
-Fluffy, relatively stress-free dramas

Main difference is that PYHOMS is in university setting to early adulthood

-Both dramas depict a very healthy relationship between the main CP.
-The two ML's are high IQ, low EQ but are gentle and caring towards the FL's.
-ML's are very serious about their jobs.
-Family issues are a thing in both.

Just be warned that Forever and Ever is the modern continuation of One and Only and while you don't need to watch that drama to understand F&E, there are very, very, brief mentions of it.