I dont know what your PC specs are but I will share my settings, I used to have FPS issues, but none since this setup:
The most important thing for me was Dynamic Resolution. For months I didnt use that as I didnt want to have lower resolution than my screen or it changing all the time, but if you set it up correctly is wont.
First of all, make sure your window resolution is the same as your screen. Then enable upscale mode, select Nvidia DLSS if possible, if not try another.
Secondly, tune the DETAIL SETTINGS, so you achieve the FPS you want(ideally same FPS as monitor refreshrate), also set the "Target Framerate" setting to this number. Tune this in a waystone, campaign or hideout, not in town!!
Lowering these settings has the most performance impact:
Lighting, Shadow + GI Quality, Number of Lights
Make sure to enable "Engine Multithreading", only enable vertical sync and triple buffering if you notice tearing on your screen.
This way the game renders at your highest resolution, until you start spamming 100 comets per seconds, then the game will lower it for a couple of frames, but that is barely noticable(I cant), because its in the middle of combat and its effects are majorly reduced by DLSS
My settings:
Display Settings
Renderer: DirectX12 (Default)
Display: NVIDIA GeForce RTX 5070
Mode: Windowed Fullscreen
VSync: Off
Dynamic Resolution: On
Window Resolution: 4096 x 2160
Upscale Mode: NVIDIA DLSS
Max Image Quality: Quality
Sharpness: 10%
HDR: Off
Scene Brightness: -3.0
UI Brightness: -2.1
Detail Settings
Texture Quality: High (Default)
Texture Filtering: 16x Anisotropic Filtering
Lighting: Shadows + Global Illuminati
Shadow + GI Quality: High
Sun Shadow Quality: High (Default)
Number of Lights: High (Default)
Bloom: 55%
Water Detail Level: High (Default)
Advanced Settings
NVIDIA Reflex: Off
Foreground FPS Cap: On — 144
Background FPS Cap: Off — 30
Triple-Buffering: Off
Dynamic Culling: Off
Target Framerate: 120
Engine Multithreading: On