The character camera is unplayably twitchy on high DPI mice, and the dev has not added a mouse sensitivity setting for that, so here's how to set it manually.

Open C:\Users\<UserName>\AppData\Local\ASPv3\Saved\Config\WindowsNoEditor\Input.ini

Find (AxisName="LookRightICharacter",Key=MouseX), and change it to (AxisName="LookRightICharacter",Scale=0.15,Key=MouseX)

Find (AxisName="LookUp",Scale=-1.000000,Key=MouseY), and change it to (AxisName="LookUp",Scale=-0.15,Key=MouseY)

I found that 0.15 worked for me, but adjust scale to whatever you need it to be.

The game will remove these changes any time you save control settings, so I've been keeping Input.ini read-only to prevent that.