This article was a timely discovery and well worth the read.
How you approach your own design with respect to resolution and screen aspect ratio is entirely dependent on your project and target device(s).
It’s because of the ever changing screen sizes and resolutions that I prefer to create my game assets using Adobe Illustrator (vector art).
It provides the opportunity to export art assets at larger resolutions later on.
There’s not a lot that can’t be done with Illustrator if you know how to take advantage of the powerful tools it offers.
The only exception for me would be when making pixel art style games, in which case I use Photoshop. You can find out what settings I use for that process here.
Of course there are no real restrictions to what you use, so long as you keep in mind the forward limitations of your choices early on during the concept and game design stage.