I've been searching for a bit, but I can't find a clear answer to some of these codes referring to upgrades at AF/KLM

Business - Classic Award & Upgrade (O) - This one seems pretty clear to me. Seat available for upgrade with miles. (which I've never been able to get any availability of on any trans-continental flight over the past 12 months )

Business - Flex Award for Elites (C) - I have no idea what this is. I'm guessing that Plat members (I'm gold myself) can apply for this award? But is it an award ticket or a miles upgrade?

Business - Upgrade with DL SWU/Global Upgrades & Fare Class (Z) - This is the one where you can upgrade with vouchers from AF/KLM or their partners I think?