My preference is the pop-up window, even with ability of opening a link in new window or detaching a tab.
The size of a pop-up is different than a window and that’s important factor. Resizing a window isn’t the same and would be a distraction to editing. And as you mention, moving it around which I do A LOT.
Scrolling vertical isn’t that much a problem if data is consistently and logically placed when initially entering and subsequently editing. And, for each of the events. Currently, they’re not but that’s a carry over from long ago too.