Wolf - circuit boards I can’t help ya with much , except to say curved traces sound better.
Now, for a simple experiment, you are a tube guy as I recall and tube amp Sonics are dominated by transformers, which you are not likely to change but get yourself a Stereo 70 and start at the inputs with a directional wire ( typically extruded in a die under a gas shield ) and work your way thru the amp.... this won’t tell you WHY...
a Hafler 200 is easy, cheap and more evident
Now, for a simple experiment, you are a tube guy as I recall and tube amp Sonics are dominated by transformers, which you are not likely to change but get yourself a Stereo 70 and start at the inputs with a directional wire ( typically extruded in a die under a gas shield ) and work your way thru the amp.... this won’t tell you WHY...
a Hafler 200 is easy, cheap and more evident