Ok, check the attached sample, is a very simple app, as you will see, there are no variants, I'm just using the designer scripts and if you have several devices you will also see it scales fine, I don't need to know the density, screen size, etc, but I know it will scale on any device.
If you have complex layouts it will take you a little bit of time to create them, but the process will be the same, 1 script and you are done.
I hope that helps.