TP2 is Technical Preview 2, it was just following on from the name Planet gave the first release (Technical Preview), and seemed sensible to keep as there are still many device features not supported. The release names are just a way of referring to the starting point, once upgraded to the latest stuff then you really need to refer to the date of you last apt upgrade to compare features available, on this basis TP2 is considered very old. We plan to release a TP3 sometime soon-ish, see other threads on this forum, hoping for a few more fixes first though, there would be no need to upgrade via the flash tool for those with working systems, its just to reduce the updates needed from a fresh install.
Interesting that your cifs didn't work with the modular kernel but did with the all-in one. Hopefully mithrandir can advise, in theory you should have access to more kernel modules and features with the module based one (the package is about 10 times the size after all). The plan was to orphan the all-in kernel in favor of the modular one going forwards, on the assumption of positive feedback, we may have to review that...
Flashing/dd'ing the boot partition manually is expected, once we get some consistent feedback of the advised 'dd' line being correct and the kernels working for lots of folk then we'll make it automatic for those with the new bootloader that knows what key combination was used to boot from. Obviously those who upgraded without going back to the flashtool will not have the new bootloader so we can never safely know which boot partition they use for gemian. Cite recent Sailfish upgrades where they 'assume' a boot partition and people lose their access to Android etc.