I have a similar issue with Topaz Studio and the Topaz plugins. If I use a color space with a wider gamut the colors are shifted. I can open a image with Wide Gamut RGB, edit it in Photo, save it as a TIFF and open it in Topaz Studio, save the TIFF, then open it in Photo and the colors stay correct. If I take the same image and send it to Studio through the plugin the colors are incorrect. So it appears to be a problem with passing the correct profile information using the plugin interface.
I use a couple of printing plugins (Canon Print Studio Pro and QImage) with Photoshop. These show up under the File --> Automate menu in Photoshop. These are very important to my workflow. Can these be made to work with Affinity Photo?