I wondered what that 'join' thing was appearing on a lot of the bigger channels. Joe has it enabled as well.
Looking at whats offered, it seems a bit stupid but I guess it'll just replace Patreon for a lot of Youtubers, so its more integrated. I think Youtube probably saw a lot of Youtubers were using that so thats why they made the changes. I looked at Joe's and you get 'loyalty badges' in live chat and comments, a custom emoji, featured comments, and then for the more expensive option some BTS stuff, polls and a monthly livestream. One option is £1.99 and one is £3.99.
I do think some Youtubers took the piss a bit with Patreon (where they could set their own prices/rewards, where it was like £1 will get you this but £10 will get you that), which made me worry some young impressionable people could've pledged more than they could afford for the better rewards, so I like that this seems quite cheap in comparison, and like the rewards are kind of 'set' at those prices. I wouldn't use it though.