the way I look at it is rank points are a all round measure how well someone is ‘out of all the current players’ at specifically ranked match’s.
50k rank points isn’t that far apart at all especially if your around rank 250K, it matters more when you get to the lower ranks with the pro’s though I believe because theres less people in the lower ranks but if you go to the rankings to your rank and try to scroll to your friends rank it may take a min because theres a lot of people in that rank
League Poionts (LP) is a measure of how often you’ve won ranked match’s reciently.
your LVL is a measure of how much you have played that character in all the exp earning modes, I think that includes all of them except trials and practice; so its basically a measure of how familiar someone is with that character. But this doesn’t mean someone who has a high lvl is going to play awesome with that character, It may take someone longer to learn one character over another, if their over lvl 100 they prolly have beaten all the survivals with that character at a guess. Generally a persons highest lvl character is going to be their favorite/most played character.