Ever since the update, walking around makes the game unplayable. I'm getting over 100 chunk updates and 5-15 FPS (unsmooth) while the game is barely using any memory or GPU and not overloading CPU either.

So it's not a hardware thing. It's either a bug within the engine or an incompatibility issue. Please take not that more than a few people have experienced this. People I know can no longer play on their own realm simply because of this update.