Friend, your CPU is bottleneck for this game.
I had same issue with my i5 4670k, it was 100% loaded, every time, with any settings.
To resolve this issue I overclocked CPU to 4 GHz in BIOS and also set 60 fps limit in the game.
Now I have stable 60 fps without drops on all maps with almost all settings are maxed in the game, even the shadows. (resolution 2560x1080)
CPU load varies between 50% and 100% (btw, smoke effect is very heavy for CPU) and GPU load is ~50%, I have RTX 2070.
Also, try to delete all config files. It helped me to resolve the performance issue with the shadows after the last update.