The Ten Thousand Beast Heaven, like the Spirit Overarching Heaven, was one of the 81 Devata Realms. The difference was more than 90% of the inhabitants in the Ten Thousand Beast Heaven were Celestial Beasts. This was due to the hatred the Ten Thousand Beast Heaven's Celestial Beasts harbored against humans and other life forms. If the beasts encountered humans or other life forms, they would not hesitate to kill.
On the other hand, the Spirit Overarching Heaven was relatively peaceful. Humans and Celestial Beast co-existed rather peacefully.