You need to set the brightness of the screen with the help of a calibration device. I recommend you set brightness to 120 cd. Brightness is not a matter of taste or personal preference, the recommended brightness in a room where there is no direct sunlight is 100-120 cd.
I think you need hardware calibration for your screen, it’s wide gamut, you should use the Dell software.
I suggest you stick to Windows for calibrating your screen and use a dual boot setup.
Edit: as far as the device model is concerned, it depends on how accurate your screen needs to be and how much time you have. The Datacolor Spyders are slower that the x-rite devices. The x-rite i1display pro is not so cheap but many calibration experts and “pros” (what ever that is) perfer it. I have a Spyder 5 and it’s enough for me, at least it’s better than nothing.
Maybe one more thing: you can use Displaycal after hardware calibration for profiling the screen.