Is SOOP the same thing as the Afreeca TV league?

Is Sen technically "defending" their title? and will it be streamed on the Korean twitch I had to make an account for last year?

yes and yes

AfreecaTV rebranded to SOOP: https://designcompass.org/en/2024/10/17/soop/

yes, same tourney just rebranded, and most likely ye same twitch account

yeah they rebranded and you need to have an account there to watch but im just gonna watch Sliggy