Everyone has different styles of learning. For me, I read the books and saw the charts and formulas, but it didn't actually make sense practically until I started building things on the bench. To see inductance and resonance firsthand and see how things like frequency affect transformer saturation. I probably learned more practical skills in a week of tinkering than in a semester worth of physics.
Tinkering certainly helps a little to understand the theories and laws of physics, but very little because it would require thousands of experiments, those done by the pioneers of physics from Galileo to Bohr via Ampere and Einstein. We would have to be as clever as they were in every field, as each one was in his own. No one has the time, the material means or the intellectual means.
If you limit yourself to tinkering without really studying the laws and theories of physics, you will understand almost nothing of your experiments.
That an electron has physical mass while a photon only has inertial mass. The implication being that a solar cell turns massless energy into mass-energy...
I'm sorry, but what you say doesn't make sense to me. The mass/energy equivalence is strict, the only thing we can say for the photon is that it has no rest mass, and since it doesn't exist at rest, it's a truism. But it does have mass, gravitational as well as inertial, since it is deflected by stars, by the sun for example, or black holes.
An amateur can still be useful to the community too because they're actually building things. Perhaps they will have an experiment you wanted to do but didn't have the time or components, or maybe they stumbled on a configuration that you never considered because on the surface it might seem nonsensical.
It is true. Amateurs are, for example, responsible for discoveries in astronomy or radio.
But how many discoverers are there? Well under 10%. Much less than 0.01%. And what proportion of physics is due to them? Even less!
It is pretentiousness to think that the tinkerer in his garage, with whom we can identify, will revolutionise the laws of physics. Even Tesla, who was not a tinkerer in his garage but a highly competent engineer, contributed a lot to electrical engineering, but nothing or almost nothing to physics. Tesla's law does not exist in physics.
So the tinkerer in his garage hoping to find "loopholes" in physics, let me laugh. I'm not saying it's impossible, I'm saying that it would take a luck of the devil, and that millions of more qualified and curious people, including a majority of academic scientists, would have a much better chance than him to discover them.
We are here to try this chance, but let's not be so ridiculous as to believe that we would have assets when we only have handicaps, starting for the 90%+ with ignorance of physics.