Is there a discord to discuss speedrunning this game? Also is this page the official release page as well?

From what I've been able to tell, this is the official/only page for BG3. There are currently no moderato's on the page to start creating the speedrun categories unfortunately.

I haven't heard of any discords either.

Haven't seen anything about Discords but I'm happy to start one up if there's demand for it. I finished the game a few days ago and have been trying to work out any% routing; currently trying to figure out the best approach to the mandatory fights at the end of Act 2 and in Act 3.

there's a discord for the other larian games here https://discord.gg/MpyuMYeH

people are still going through their first playthrough

Taking my sweet ass time with the first playthrough, but excited to try some runs later this year. This game is too good to rush it imo. Probably most people are still at this stage.