Best Lakorn: In terms of storyline, I'd say Roy Marn but in terms of overall performance, chemistry, interactions between the casts, dialogue, OST and memorability, I'd definitely pick GRGR. Having that said, my "favorites" go on in this order --
Game Rai Game Rak, Roy Marn, Plerng Toranorng, Tawan Deurd and 3 Num Neur Thong.
Best Couple/Favorite Couple - Without question, Nadech & Yaya. I do adore Mario & Taew as well.
Couple that should pair up again - Since Yadech and Bargie are reuniting again, I won't bother mentioning them. I think Mario & Taew deserve another lakorn together because I personally think they do have potential to be a good pairing but unfortunately, the storyline of Plerng Toranorng didn't allow them enough screen time and their "sweet scenes" were very limited.
Couple that shouldn't pair up again - I won't chose simply because I'd like to give every pairing a fair chance. But I will say that the most disappointing couple for me was Boy and Marie. They had zero chemistry IMHO but I'd put some of the blame on the lakorn itself.
Future Couple - Considering how Ch3 likes to mix match between pranangs, I'm sure all of them will cross paths with each other one day. I do hope to see Nadech & Taew, Mario & Yaya and Boy & Kim.