Beryllium copper vs spring steel makes a big difference in the resistance of the spring. Gold plating does not. The gold plating is so thin that it does not contribute to the conductivity of the spring wire. It may improve the contact resistance, but with spring steel wire that's usually trivial, especially vs nickel plated wire.
In my experience I've found that beryllium copper springs are rare and expensive. Spring steel conical springs are high resistance, even if gold plated, due to the long, low conductivity wire that the current has to pass through. My favorite configuration is tin plated bronze or brass leaf spring. The conductor is short and wide, giving low quite low resistance. The drawback with this configuration is that you have to provide mechanical stops to prevent the leaf spring from getting crushed.
The leaf spring works great in some lights, but in some the conical spring is just unavoidable. If you must use a spring steel conical spring in a high current application, the resistance of the spring can be quite significant, and a bypass may provide significant improvement in performance. Not speaking from experience here, but as an engineer it seems to me that the bypass should be as close to the battery and the negative rail as possible, without interfering with the contact at the battery and negative rail.