Oh you have come to my specialty ;-) Before I did software...I made Volvo brakes...
www.upbrakes.com
The 366/340 (F/R mm) brakes are just a rotor upgrade for the heaviest model, the largest PHEV: XC90 T8, as far as I know they are only used on that model but there may be others.
Physically, you can swap these brakes, super easy! If you have the 345/320 brakes, the calipers and pads are the same as the 366/340. All you need are the caliper brackets and rotors to do the swap. I've done both front and rear upgrade to "T8" brakes on my S60. If you have the smaller series 322/302 size rotors, the calipers and pads differ so an upgrade there would require new calipers and pads.
I have my own brake kit in the front now, which is a fixed caliper, using the OEM 366mm T8 rotor. I continue to use the OEM 340mm brackets and rotors I swapped on the rear.
For the electronics OrBit part of it, the brake settings are there to change the fitted brakes. I think someone tried and they got DTCs that would not go away changing the brake size settings. I haven't tried on my car, I should probably test that ;-) I think the size setting may re-calibrate the ABS (and the many other brake based systems) slightly, for the larger rotors, which will produce an increased braking leverage vs the 345/320 brakes.
FYI - Some people are not familiar with the example: '18" brakes' type terms that OEM mfrs use. That spec refers to the "smallest wheel that will fit over the brakes" it's just a sort of industry shorthand to refer to brake sizing that is used all over. The 366mm brakes for example being classified as 19" brakes, they will not fit inside an 18" wheel. I have 19" wheels on my S60, so that was no worry for me doing such a swap.