1) How do these two interact?

A) Keep the chosen supply chest card and the chosen stockpile supply card (2 cards total)

or

B) The chosen supply chest card is simply added to the choice of 5 supply cards, keep 1 card (1 card total)

2) Bonus question: How does Stockpile work when interacting with crates in the app?

2) When the app says to draw a supply card, a) see if Stockpile can be used, b) choose whether to use Stockpile, c) if using Stockpile, draw 5, and choose one non-valuable to resolve/keep.

I'm pretty sure the intent of Stockpile is to not resolve any of the cards until one is chosen, so:

1) When you draw 5 supply cards with Stockpile, you choose which non-Valuable to keep. If you choose Supply Chest, discard others and resolve Supply Chest.

What about when the app has you draw two supply cards? Would you resolve stockpile separately or keep two of the five cards drawn?

If you get to draw 2 supply cards, you first get to draw 1, and can choose to use Stockpile instead. You then get to draw 1 supply card, and may choose to use Stockpile instead.

Okay thanks @a1bert , that’s what I thought.

Supply chest is a V aluable card. If it came up in the Stockpile draw would I resolve it's text as written immediately (basically replacing it with 3 other supply cards) and then proceed with choosing one of the (now 7) non-valuable cards? Or would it simply be one of the 5 cards to choose from and be rendered an invalid choice because it is valuable?

Rules as written with the original wording: discard Supply Chest, draw 3, choose 1 to keep, return the 2 others, reshuffle the deck, continue drawing to get 5 cards for Stockpile, choose one of the cards to keep and shuffle the rest back to the supply deck.

The FAQ wording changes Stockpile to also be app-compatible, and should answer the question directly, because only one card is actually drawn:

Stockpile :

“When a friendly figure within 3
spaces interacts with a crate, instead of
drawing the first Supply card, it may
look at the top 5 cards and draw 1 non-
valuable card. Then, shuffle the deck.”