Hi there, small an short for a (nearly) constant and smooth gameplay feeling…
i tried nearly everything for optimization what u can read in the net an in the forum!!!
But nobody thought about the PC bios, what it does before u set specific settings…
For short - enter ur PC Bios and DISABLE the CORE BOOST option.
it is a simple option which has control how fast ur cores are running.
Set it to DEACTIVATED and set your CPU MAX Frequency manually.
That sounds very crazy, but try ur luck with it, u will be able to see ingame that the fps is nearly constant on fields and in town about 26-34 fps due to the other players.
My fps are mostly between 57-62 fps outside of town.
My user.xml is now in fullscreen(1), V-sync on, Bit per pixel 16 an resolution 1920x1080…
Maybe it will help a few of u.
My specs are : Amd Athlon X4 880k BE
8GB DDR3 1600
RX-460 2GB DDR5
50mb/s Germany/cologne
Like i said before, MY gameplay is MUCH smoother since hours before, but the other things are Programmer sided things 
Its only a little help to a few other ones.