I realize this is an old thread, but I am having the same issues with my 295x2. The second GPU fluctuates both in speed and usage and causes very noticeable FPS and stuttering issues. Not sure what to do about it as games like Titanfall2 and Deus Ex Mankind Divided are unplayable with CF. I have it disabled for now, but it is frustrating.
32GB DDR4 Ram
Samsung 850 PRO