Hi Fifi , thats exactly same problem i face with my rig
i5-8600k 5.1 GHz
16 GB DDR4 2666 MHz
NVIDIA GTX 1060 6GB
SSD
Windows 10 Pro
I have beautiful graphics in SH5 and no lag , in SH3 i just cant get any AA to work with it , i tried Inspector , Nvidia control panel .. , Override , Enhance nothing... nothing works it just horrible all the jaggies burns my eyes!