location of pressure switch
Not really that critical.
While it is generally preferable/best practice to put the pressure switch at/near the pressure tank, it will still work if it's not there.
The pressure at the tank may not match the pressure at the switch, but for the most part, that rarely matters to the extent that it's not the same, in a system with reasonable pipes (size and condition.) If the pressure at the switch is 30/50 and the pressure at the tank is 35/55 or 25/45, you still get water, under pressure.
The default 20PSI differential/hysteresis tends to protect against small effects that would be difficult if the differential was not that large.