I love the Road to Legend app for Descent but I would really like to have a look at the MoM app, what the 1st edition expansions add to it and a little gander at how it actually works before I lay down close to a $100 for a game I sort of already own (1st edition and expansions).

Is the app going to be released on the same day as the physical game or a little earlier?

Looks like they will be released the same time - you need both physical 2E and the app to play (technically the app is a necessary game component that doesn't happen to come physically in the box).

The XCOM app released a week or two prior to the physical game being released, so they may release it earlier in this case too.

However, I don't think the XCOM game had such a specific release date like this one, so it may be they're timing it to release on the same day.