@rrocan – Great additional feedback. As we go forward our plan is to definitely offer more flexibility in those areas but doing so is a bit tricky.
To be clear what I mean is before we dealt with the content editor. Now we are gonna deal with page builders and the new Gutenberg editor which means much of what you want would be handled in those. Determining a proper size in any automated fashion is rather difficult. But our responsive sizes try to do that.
That said I believe you probably used a default responsive sized Popup. The width is set there by % of screen unless on mobile screens then set to ~90%. You may have preferred custom which allows setting a specific pixel height and width to match your image for example.
Further padding is part of the Popup theme, not the popups own settings. So you can set it to 0 via the Popup theme editor and eliminate it that way.
Hope that helps next time around.
Hopefully we can make it simpler going forward. But due to the varying degree of what you can insert it’s hard to make a 1 size fits all solution.