Templates and frontend posting

Hi, I am a new customer of the premium version, so I apologize if I miss something but I need to have a better idea f what I can de, asap. I have a membership site with full control on roles and capabilities. My website is frontend only, I use a frontend posting plugin that supports attachments, CPT and custom meta if needed. From my understanding, media, galleries and albums are all CPT, so it should be possible to integrate my frontend posting system with GMedia gallery, but considering that Gmedia are not standard attachments, I need to understand how. How do relationships between media, galleries and albums work? Are Gmedia automatically attached to each CPT? With what kind of relationship? (please note that I also use ACF, just in case this can help). One more thing, would be possible to add a shortcode to my templates to display current user galleries / albums? (usually a snippet to change the default WP_Query filters does the trick). I see that by default the user must be selected in the query, or it automatically gets the_author or the user nice name? Is there any documentation about an API (if any)? Thank you very much in advance.