@ReyCBXZRX
I don't always follow the logic or English of what you write, but never mind :)
A QSpinBox has a pair of "scroll arrows" at the right but it is not a "scrollbar". These are for inc/decrementing the number value and have nothing to do with scrolling or sizing. A QLineEdit is for entering text (rather than number), is single line and has no scrollbars. A QTextEdit or QPlainTextEdit is for multiline text, can be resized vertically and can have scrollbars.
There are two ways of adding a layout to a widget in Designer. Each widget can have a layout set by right-clicking on it and selecting Layout > menu item. However for unknown/inexplicable reason this is only enabled when the parent widget has had at least one child widget placed on it, you cannot do it before you add any child widget, which is rather odd. Alternatively there are explicit layout items available at the top of the all the items you can drag from the left-hand side toolbar, these can be dragged and placed anytime. I have never understood/investigated whether there is any difference in result between these two methods.
With layouts there should be no "overlapping", it is their job to prevent this.
One tip: If you look at the Object Explorer --- the pane at the right which shows all your placed widgets in their hierarchy --- you will see a "red no entry" symbol on any widgets you have created which do not have a layout but should have. If you see that you know you should be adding a layout there.