Jon,
This is the sort of thing that is like trying to describe to someone what an orange tastes like. It's impossible to pin it down. But then if you talk to someone who has also eaten an orange then it is possible for them to communicate about it and understand each other.
Here's my take based on eating oranges. :

Bliss overwhelms me. It is emotional and physical. If experienced around other people you might find yourself looking around to see if anybody is noticing your bliss.
Joy does not overwhelm me and is a much calmer feeling. It has a sense of accepting everything just as it is. As if it was always meant to be that way. Even people and things that may have annoyed you in the past, you will find that they cannot be any other way then the way they are. In some sense then maybe Joy affects my mental formations too.
I hope that you and anyone who reads this experience both in abundance.
Gerry