IMHO, OK and OK+ are the best combo by quite a margin for intra-Europe flights (and AFAIK the only FFP that will give elite upgrades within Europe).

Unfortunately, they don't fly to NAP!

With AP merged into Alitalia, I would make do with them- they are not THAT bad, and they're more likely than LH to carry out a request for something you are not contractually entitled to.

In terms of which FFP to choose, you need to be VERY careful, since some airlines offer reduced mileage for some classes in some programmes. It would be entirely possible to take a whole bunch of AZ flights and have nothing to show for it in your Delta account...