Thank you very much to both replies. I still find this technical stuff a little bit foggy, but the further explanation of "stokerg" reply's by "SrPx", does give me a better understanding of the matter.
If I understood correctly, to get the most ot Affinity Photo, I should set it to work with my CPU. I suppose I could fine tune a better performance directly in Affinity's Preference Menu.
Also, if I didn't misunderstood, the GPU might be of some help of sorts for performance, but since it's a laptop version and also an old model, the boost in performance might actually be a very small one or maybe even none at all.
I consider my question answered, but it begs the question, if Affinity does work better with CPU (like brushes which are one of the main features I use), why have a screen selection to chose between CPU and GPU? In which case does using a GPU is beneficial for Affinity Photo?
Thank you both