I have been using Affinity Photo 2 exclusively since April, aided and abetted by DxO PureRAW. It was not the price that made me leave Adobe, but that is perhaps for another topic.
Affinity offers a choice of using Apple's demosaic or Serif's own. I have only used the latter and it is very good, superior to Adobe's standard version.(Their Enhanced Details one matches it.) They obtain profiles from the LibRaw database. Lens profiles come from the LensFun database. I have not been paying attention to how up-to-date they are because everything I use is covered.
DxO PureRAW provides that company's excellent raw conversion, lens profiles, deconvolution sharpening and noise reduction. A bonus is that their noise reduction is much, much faster than Adobe's and provides a nice, big preview.
Affinity is not as good as Adobe at recovering highlights when converting the raw files, but it is only noticeable when trying to rescue, for example, an overexposed sky. Pay attention to your exposure, protect important highlights and you will be fine.
There are a couple of other differences that spring immediately to mind. ACR makes it easy to copy adjustments from one raw file to others. Not so in Affinity. It can be done but it is cumbersome. Affinity is very much designed for concentrating on one file at a time. It also has nothing like the various "camera matching" profiles that you will find in ACR. The raw converter gives you a nice, neutral image for further processing in the main part of the program. I find that +10 Contrast (either in the raw conversion or as an adjustment layer) gives me something close to Nikon's Standard profile. Oh, and there is no sharpening by default. That too is left to you.