I did some benchmarks with absolutely no clouds (preset nothing + cloud density 0) and it looks like the new engine is more gpu friendly than cpu. I gained 11 fps on high and dropped a lot in low and medium. Its still very playable even with clouds on, with no stutters at all, but I share with you my numbers if they can help.
I benchmarked using gryz mission from user files (complex version), calculated the average fps with afterburner and did multiple runs per preset with the same settings to see if there is some variations (+/- 1fps every time).
Windows is fresh, drivers up to date and I made a new saved games folder for the tests ..
Average fps for each run
GTX1080 R5 5600X @1080p
2.5.6
2.7.0
Low
221
164
Med.
192
144
High
72
83
High(no sslr/ssao)
106
91