Both options will be "primary" in sense that both will be equally supported and encouraged. We just want to make it clear that one does not need to own N900 to be able to benefit from Neo900, or you don't have to cannibalize your N900 if you want to give Neo900 a try.

Even despite of us stating at each step that it's going to be a complete device, some news on various sites stated that it will be available only as mainboard replacement, which is plain wrong.

Of course if you're interested in just a mainboard to put it into your N900 shell, you're more that welcome to buy it cheaper than complete device and do that! Everything you'll need to do that will be included in the package and whole operation should be reversible (except making hole for USB connector slightly bigger to fit OTG socket, but I don't think that's a major issue)