The only thing AceGUI (on its own) really does is allow you to reuse frame objects instead of creating new ones. If you have three options panels, each with two checkboxes and one editbox, normally you'd create a total of six checkboxes and three editboxes. If you use AceGUI, though, assuming only one panel is ever shown at once, you're only creating two checkboxes and one editbox, and each time you switch which panel is shown, each of those objects is reparented, resized, relabeled, etc.
If you understand the basics of config widget creation and manipulation, it's generally about a thousand times easier just to create six checkboxes and three editboxes. The "extra" memory usage is really not significant in the grand scheme of things.