I tested this on multiple computers.
One had windows 7, core i5 7500, nVidia 1050 Ti.
Another had windows 10, core i5 8600k, amd rx 580.
A laptop with core i7 8565U, Nvidia MX 150.
I was recommending Affinity to few other designers and got similar result from them. It made a very bad impression on them because of the slowness. I tested with multiple affinity trial, stable and beta versions for 1.7. Cleaned windows and so on. Surely if 5-6 computer does the same, it's not a computer specific problem.
From what I can understand from all past posts, this happened many times for windows users. It's hard to debug a windows version because of so many variants of available configurations. But I can see the patterns here.
Most of the time it uses CPU and not the GPU. Rendering is a normal stuff, but the weirdest part is, the GPU is not used even 10% (on nVidia and AMD or any other pc), when I work on a layer with effects, while CPU goes like 60-80%. Sometimes GPU is completely unused (not even 1%).
Doing anything (ie: moving elements) renders the whole canvas. The bigger the canvas, the slower it renders. No matter what performance settings you try. Slow rendering happens on inkscape as well, but you can tweak some settings to make it behave more like illustrator and show outline when moving instead of rendering on every action.
Here is the typical CPU and GPU usage on a graphical program during moving/zooming/anything triggering a render. You would assume it would be the other way around.
Trying same thing on illustrator but GPU is used properly. And it looks better as well.
Here is a video of how a sample file looks on inkscape, illustrator and designer. Now, how do I convince someone to ditch illustrator for designer if the UX is so slow. Sometimes money is not the issue but UX is.
Maybe I can convince people to use Affinity if it works properly without lag and so high CPU usage.