My question
Which one do you consider the regular one? was regarding your use of the term
widget, which I understood to be used for sources, or even other parts of the software like scripts or plugins. I'm sorry if this lead to even more confusion :( You are right that the wiki is not the best documentation...
Maybe it would be useful to crop te Window Capture source? Hold down Alt while dragging the red boundary (it'll become green then).
See the Sources Guide. Please keep in mind that the aspect ratio can change due to cropping, potentially leading to black side bars (either horizontally or vertically).
Feel free to ask more!