Jon,
The term "Performance Enhancing Drug" is vague. If we have a PED, there can be no doubt that it is both a drug, and performance enhancing. Otherwise it would not qualify as a PED, but simply PE, or D, or perhaps neither. The question lacks precision, therefore the answers will too. The only answer to your question is "it depends on the drug, and the person".
So part of your question, I guess, is "do PEDs exist?" Then, "if so, which drugs, and for whom?"
Do you honestly suggest that NO PEDs exist for anyone? Do you suggest that anyone else, outside of JR, agrees with this? Do you suggest that science generally agrees with this?
Despite the existence of bio-mechanical efficiency, performance is also partly bio-chemical.
If some imbalance or weakness exists, and a drug strengthens that weakness, bringing more balance, then performance will improve. At the top, athletes have more balance, and fewer and less severe weaknesses. Yet even top women will respond well to male hormones, for events requiring muscle strength.