Can I set my MuchBetter card as my default Apple Pay card?

Yes.
To make your MuchBetter card the default:

iPhone

1. Open Wallet.
2. Touch and hold your MuchBetter card.
3. Drag it to the front of the stack.

Apple Watch

1. Open Watch app on iPhone.
2. Go to Wallet & Apple Pay.
3. Select Default Card → choose your MuchBetter card.

Note: Apple Pay is now supported in Canada, Israel, and the United Kingdom. We’re working to bring it to more regions, so stay tuned for updates.