What driver versions are you running?
I observed these issues with 417.11. I can try 418.81 which is the latest version. I can send files over if it is helpful. This is on a fresh install on a standard SATA 6GB/s SSD, RTX 2080 with slight overclock, i7-7700K @ 4.5ghz, 16GB of RAM @ 3.2ghz. I am not thermal throttled on anything and the hardware on either CPU nor GPU gets anywhere close to full utilization. I am using the exclusive fullscreen launch option also.
With Special K (same guy who made DSFix for Dark Souls 1) frames go from like 30-80fps in busy maps like Queen's Berth @ 1440p to 80-100fps+ on high/ultra. None of it fixes the stuttering, but the FPS is higher. Seems confusing if you are not experiencing stutter considering how many people here and on reddit are experiencing the stuttering behavior. To make this clear, the FPS will stay at whatever it is capped at more or less (100 is what I keep it to), but occasionally there will be a frame stutter for around 300 ms.
You can either use a hardware monitor or the Special K overlay to show you at what times the frame stutter occurs and for how long it persists for. The overlay has a chart also that demonstrates when the stutter occurs.
Stutter appears to be more frequent when there are many actors on the screen and it "feels" like it occurs more frequently when using Fast Mode, but I can't say for sure because I haven't logged anything.