Pixels Pro was advertised in the iTunes App Store as a "powerful graphics editing program". A high claim, which I found to be untrue.
Pixels Pro was on sale for a limited time, so I decided to try it as a painting tool. It turned out that, on the original iPad, at least, it's not really suited for that. I don't own an iPad 2, so maybe it's tested and tweaked for that device. The further I went along, the slower the app got. I suppose it's all the undos. As a workaround you could save the artwork in the gallery and then edit the saved version.
I'm sure as an editor it is great. As a drawing/painting program it's below average. Procreate is much better, although it has less features. Features isn't everything. In fact, you can have too many of them.
I took a 1024 x 1024 canvas and a photo as the basis for my paining. I drew an outline on top of the photo (in a separate layer) and used several layers to add digital paint, after which I made both the photo and outline invisible in the final output.
Unfortunately, 1024 seems to be the maximum value of either width or height, which makes editing photos not very useful, since most photos are much larger than that (at least 6 megapixels, which is one-sixth of Pixel Pro's pixel count). It outputs a lower resolution than the original and that can't be right.