NY/MK -- we don't know what they experience everyday to 'fall in' love. We can't assume that they hang out and end up together. If that's the case then there's no 'friend zone' but bf/gf zone only lol.
Actor and actress have all kind of potentials. It's really up to the director to bring that out of them -- Even Mark said it himself that he could not imagine playing such harsh role and so does Yaya but because of the director and p'Da that's why they became Jee and Sathit. Bias or not, I believe that Nadech has that skills to back him up. If he's with a good director and producer, he will outperform himself just like many of his solo works. I believe Yaya broke out of this character because of p'Da's demand as well as p'Aew's ability to direct her better this time than when she did with her Nangfah's character. In Nangfah, Yaya's world is 'innocent' so it makes sense why she was a bit childish in there - a bit bunker due to lack of character .. but Nadech is none to be fooled. He has his skills
As for height, I believe Mark is just a bit taller than Nadech but not that much. With heel, Yaya's is probably 5 fingers away from him as well as a few fingers from Nadech.
I'm not here for fanwar but the previous writer did write that Yaya is stuck with NADECH because they basically 'EVERYWHERE' together. There are other koojin who did not date even though they work together too -- look at James Ji and Bella
If people fall in love and are together 24/7 ... it is because they are in love. I'm going to use p'Marsha' word 'don't be too "in"' to not notice reality. Of course, they're still young and things may change but at this moment she loves him and he loves her .. Between them, they know it better than us fans lol