The main difference between other plugins is that Rexy is the first that offers ACF Flexible Content. Also it implements the functionality’s in a truly 100% way, which means it is build upon the existing widgets of Elementor. So no need to user other widgets than the ones you already know.
This has a couple of benefits. First if you already have a website site up, you can just simply connect those widgets to Rexy. Also you don’t have to explore new custom widgets. Rexy comes with two extra widgets and those are more containers for the Flexible Content and Repeater Fields.