You basically quoted thin air: "more features [...] for a wide range of advanced editing tasks". You probably know more than what's written there, but from my perspective I haven't learned one concrete feature that PS offers over Affinity. It's typical SEO spam, which rewards swaths of text with little to zero information density.
I’ve tried learning GIMP, and it sucks. I’m not saying GIMP sucks, but you have to be crazy to not see that it’s hard to learn.
I use GIMP for memes and here's my two favorite tips
Hit the forward slash key / to open a command palette and jump to any action
To remove backgrounds, use a layer mask. select around the object and paint a white/black section on the layer mask. Here comes the trick: use a Gaussian filter on the layer mask to create a transition from black to white and the crop job looks a lot less choppy.
My anti-tip
Adding text and shapes sucks and I never found a way to make it better. Export your image and finish the job in Krita, Pinta, Photopea, ...
this is the first i hear of Arc, is it available as an iOS app only?