Customization options can be found in the theme customizer.
Typography, colors and general UI elements
These options are global and apply to all app blocks.
To find the options, go to > App embeds > Try On Settings:
Functionality
Add the app block extension to the page you want to show it on and you’ll find options for functionality.
These apply only for the selected app block.
Text
Full text customization is currently not available, but we’re working hard to make this happen very soon.