Kraig recommended this software. And I’m going to buy it. CAD $55.
Pixelmator Pro is Mac only. It supports the new (2020) M1-chip and macOS Big Sur.
Below is a Pixelmator edit of an iPhone X 4K original. I followed the official tutorials.
What you see below is a smaller version for web. But if you click on it — you’ll be able to see the full size original.

I’d long wanted to quit free Apple Photos software that comes with every Mac. Never liked it. Unfortunately Apple keeps you locked into the ecosystem. Happily, Pixelmator Pro works hand in hand with the Photos app. No conflict.
I’m also tested the Sony Imaging Edge software (horrible) and Capture One 20 Express (free). But Capture One 20 non-Express is too expensive – at least $10 / month.
I have Gimp (free) but find it pretty complicated.
This video show the fantastic interface of Pixelmator Pro.
Click PLAY or watch it on YouTube.