I have been using the Auraspeed 100x in 3U, extremely easy on the arms and believe me. You can drop some bombs with this racket. 4u might be on the light side also with the racket being head light.
The Original JS10 3U was one of my all time favorite rackets. If you like control, I would recommend a Li Ning Halbertec 8000 3U. I recently got this racket and it reminded me of the days I used the JS10. Defense and drop shots are super easy to do, smashes need a little more effort but still very solid.
It has been many years since I used the JS10 so you are probably right. I cant really handle stiff rackets anymore. Probably why the H8000 feels nice to me