Hello,
First of all, if you are concerned with how to display data in your own HTML markup, the best way to do this is by overriding the templates. Since 5.0.0 this is done in a way that is standard to WordPress, i.e. you copy the template files and hack the markup, placing the new files under your theme or child theme. For more information please see the relevant release notes, and the accompanying documentation.
Regarding your question about API docs: There are two major APIs to the plugin, the PHP API and the JSON API.
The plugin’s documentation is found in the bundle download of the plugin, which you can get here. The same is true for the Exchange extension, which also has a bundle download. Both bundles include a PDF document which includes documentation on the JSON APIs.
Additionally, there are instructions on how to communicate with the API using a bearer token from the command line using curl. Instructions are given in the JSON API page and in the documentation. The user can display or refresh their bearer token using the [wallets_apikey] shortcode.
Using the JSON API you can construct any kind of interface including web interfaces or standalone applications. Additionally, you can call the JSON API from any programming language where you can do HTTP requests and parse JSON.
Have a look at the docs and let me know if you have any questions.
I have began dev and will be releasing plaintext shortcode outputs over the next few days, but this can only be implemented for shortcodes that output simple values. My recommendation to you is that you first look into the templating system, before attempting to hack a new solution using the JSON API. But it’s up to you.
with regards