We usually eat that strawberry (or other berry or fruit) soup with cream or milk as dessert itself as it´s quite running. But of course if you use more potato flour, it might be good also for cake filling.
Yes, or otherwise condense it. Then if it's thicker consistency I think it would make it as a cake filling. I maybe will have to experiment with this idea. Or it could be a way of flavouring the cream. Like cream mixed with some strawberry (for example.. But many other fruits also) purée and add some of the raw fruit chopped for texture.