I just came from using software that could edit PSD files but when it came to export, it would flatten all the objects in each layer and convert the layer to a bitmap(!) Now that's pretty bad... I do have a photoshop trial running and it's a resource hog for sure. I did find out that as I create flyers for example, they can still change the text, they just have to re-write it to whatever they want with the same free font I provide and they use the same color. Works well. My other option is to just change the text for them as many people don't have the software to begin with to edit.
On another note, I'm wondering if there is a licensing/legal matter on being able to export everything to 100 % editable PSD files...? It might not be Affinity Designers fault. Not sure. It a shame everything has to be dictated by PS. No competition means no progress.