I always thought that a key for one good relatashipion are little things. Little things you do, you say, you notice. That means that that person actually pays attantion on you and listen when you talk, and than you can debate over it. It's normal to have fight over it, but on the end they always come to the same term, just on other way. (Snowbarry 1x12, Snowbarry 4x13)
If person understands you, or at least tries to understand you, that means he deeply cares about you and he wants to know more about you. Your likes, and dislikes. Your hobbies. (1x03, 1x05)
If he can make you laugh no matter how uncomfortable and hard some situation for you is, than it means he loves you better when you and he can't stand to see you sad and he will do anything to make you happy (2x22)
Finishing eachother's sentences means that your minds works and thinks the same way and you can always find a common language and always understand eachother (most of the episodes)
Or that's at least how I see things.
And there is so much more then thoese things that makes Snowbarry a perfect couple for me. They are perfect candidates for a couple and I would for sure love to hear and see their's love story😀