The problem reoccurred after a while, perhaps when updating the NVIDIA driver again.
After researching more thoroughly and realizing that it was only a limitation during matches or in the game itself, as the FPS was normal in the menu and in the Training Grounds, I found a key in regedit. When I deleted it, considering the full installation path of BF6, everything returned to normal and the FPS is now working properly in the game. This is the key:
HKEY_CURRENT_USER\Software\Microsoft\DirectX\UserGpuPreferences
It must have been some conflict or the registry was corrupted. Well, problem solved to me!