Hi there :)
I bought affinity photo and designer few weeks ago hoping to shift permanently from Adobe. Unfortunately, both affinity programs appears very slow and poor performance to me. Especially, when dealing with raw images of 30 mb. It takes more time to load a raw image which is very bad. (much longer than adobe). While working on the image when any slider is varied the image jitters and processing takes long time like square boxes appearing and disappearing and then the image is back again with the applied controls. Some times it take so long that the program becomes unresponsive. Any help will be appriciated but I think its the program and not on my side. My machine specs are as:
Windows 10
core i5 (7th gen)
amd radeon R7 (4gb ddr5)
8gb ddr4 Ram
Full HD