Hi, I'm glad you're interested in watching 6v6 mk8dx streams. The score on the bottom of the screen is usually displayed by a tool called MK8DX Scoreboard, which is a program that allows streamers to show the score, the players, the teams and the tracks of a 6v6 match. You can find this tool on this website :
https://www.mk8dx-lounge.com/, where you can also download it and see how to use it.
The MMR and rank icon are usually shown by a tool called MK8DX Lounge, which is a website that hosts online tournaments and leagues for mk8dx players. The MMR is a measure of skill that is calculated based on the results of the matches. The rank icon is a symbol that represents the tier of the player, which ranges from F to S+. You can find this tool on this website :
https://www.mk8dx-lounge.com/TableDetails/50814, where you can also see the leaderboard, the rules, the events and the tables of the tournaments and leagues.
I hope this answer helps you understand more about 6v6 mk8dx streams. If you have any other questions, feel free to ask them on the forum. See you soon!