So what I ended up doing (following the tips from @victordcq ) was to create a custom css file with the following lines:
.ia_popup {
width: auto !important;
}
To sum up :
The resizing of the popup works perfectly fine as long as you dont move the pop up .
if you open the pop up and move it and expand it, it doesnt work, same if you open , expand and move (regardless of what container type you use) somehow the width and height of the root container gets overwritten (some width is assigned to it )
The solution is to use css line mentioned above.