A new interview yesterday said they cut Darcy, Jimmy, and Monica finding the Darkhold and battling Scratchy (the rabbit), a demon , because of the time it was taking for CGI. But it doesn't seem like there was much else cut from the "finished" story. The same interview also said they originally wanted to release the first 3 episodes at launch which explains why they are slightly different.
A tenth episode likely came from an original plan to do 10 but not finding enough content/story to do it so it was trimmed to 9.