Have you got any ideas on how to achieve this kind of interface that pops up at the 3d space? This image is from the archipack addon. I've read the script and the panel itself is found on the 3d space UI and wondering how he created this type of panel with layout design and interactive buttons inside the panel.
You have to draw the interface yourself in a modal operator. See the modal operator template in the text editor, and use the bgl module to do the drawing.
You may take a look at asset flinger implementation.
Asset flinger github repo
As a side note, bgl module is currently not supported in 2.8 series and a complete rewrite is planed, so this api is likely to change.