Pastihea has 2 fuses. One each for voltage 1 for 110V 1 for 230V So it's enough that you only replace one for your voltage 315 mA slow blow for 230 V 630 mA slow blow for 110 V

Yes and this is not a issue... Every US 5 PRO works this way. This is how the volume control in PRO is designed. (resistor ladder) (256 steps by a reed replay attenuator) For "silence" you have the normal US 5, which has an classic ALPS RK27 potentiometer

I had similar feelings

Have the same in Morpheus MKII. Every Morpheus MKII mainboard looks like this. I asked Sonnet about it and got replay from Cees that is normal and it's MKII 'feature'. "This is a noise improvement on Morpheus MK-II"