The game DOES USE/APPLY Playstation HDR Calibration app settings.
Unlike previous game, DS2 will correctly read and apply system level HDR Calibration values so you basically don't need to adjust anything HDR related in-game....except one thing.
The HDR Luminosity Settings slider will basically control HDR contrast and with this game's HDR implementation it could have sense.
By Default 5 the game can already reach perfect black levels in many occasions (especially in closed areas) while in open areas black levels are often quite lifted instead, meaning this is creator's intent anyway.
For this reason I recommend leaving it to Default 5 but if you don't like the lifted blacks while exploring outside you can decrease the slider to 4 or 3 (but don't go lower than that or you may crush details too much)
BONUS:
On Consoles: use Performance Mode for best fluidity and input response at 60fps, while it will still look good on base PS5 and even better on PS5 Pro