I used the Xbox Store PC app to move the entire game over to the new SSD instead of reinstalling. Took a couple of hours (!) but worked as intended. A first quick test like above show about 5-7 FPS on average better performance and reaching higher FPS overall. Also the game loads like 30% faster which is nice in itself as the game takes loooong to load 
Coclusion: I’m happy with the new setup. Thanks for the help.