[dwarfnebula]

I bet savings of rotating mass are worth more than other weight savings, but if you put too light a flywheel on that thing you may have to bump the idle up to compensate for the lost inertia, which would probably defeat the purpose. Part of the point of a flywheel being heavy is to have some inertia to smooth out the motor at low RPM. The stock one isn't probably very heavy anyhow.

As to the cam gear, since it's spinning 1/2 of engine speed, very small in diameter and the stock one's pretty light to start with I expect any difference would be practically impossible to measure. Don't put one on unless you're sure about it's quality, I'd hate to have it come apart and bend valves for you. I've had some bad experiences and have become very picky about where I source timing components.

You said you like to improve things, in either of these cases I'd say you need to consider what your objective is. Neither a heavier nor lighter flywheel is better, rather a heavier one is better for one set of requirements (idle stability, smoothness, stall resistance) and a lighter one is better for another set (responsiveness, high RPM performance, maximum power) and that's just how it affects how the engine runs. I would bet a lighter flywheel is more prone to overheat and chatter, though I have no data to support my hunch. I know for sure though, there are lots of trade-offs and what's "best" is variable and based on your requirements.

X2 on the lightweight wheels. Cut down rotating mass where it's heavy and big around first, I'm confident that's where you'll see the biggest gains for the least effort.