You can change it under your account options.
To change them individually, click on your username at the top right, and then click on "edit subscriptions" under your avatar. Click on the pull downs for each subscribed thread and make the changes there.
It looks like the combined digest is the default email notification. You can change that under "edit account details".
But I did prefer the old way of being able to select how notifications would be when subscribing in a thread. Rather than going through an additional step through account preferences.
-Ed