Average mini app UX should start with as few buttons and UI elements as possible.

CarPlay UX is a good starting point, and then slowly add functionality.

https://www.google.com/search?&q=carplay+ui&udm=2

Of course there are plenty of instances, e.g. games, where the UI is denser and more complicated.

You'll get the most people to add the mini app if you just prompt.

what are your thoughts on the Add Mini App CTA modal?

When the modal opens immediately on entering a mini app, it feels too soon and abrasive. Putting it further in the user journey likely decreases mini app adds I’m guessing?

Where would you put it?

-- CarPlay UX is a good starting point,

Clever analogy.

Striking to have one button per screen with

Striking to have one button per screen with https://yellowme.xyz

Nothing worse than opening a mini app and getting hit with a million buttons and no clue where to start. Keep it stupid simple in the beginning or I'm gone

Agree. I say in most cases, less is more when it comes to a good UI; reduces visual clutter as well as cognitive overload.