Both pins of my schuko sockets live?
there is an improvement in sound if all the electrical components - amps etc - are the same polarity


If there was any improvement, the corresponding equipment can be considered severely broken - because it is not properly isolated from mains voltage. Mordern equipment uses switching mode power supplies anyway, and the secondary side should be referenced to PE - protective earth.


  electricians screwdriver [...]
  I get a light from both holes [...]


Those lie to you all the time. The light is really high impedance - ususally 1MOhm - and can be triggered by capacitive and inductive coupling. Do not rely on them.