If you are looking for UBoat action, in my opinion, you have to do Operation Monsun from Lurker_hlb3 (of RSRDC fame), in spite of some 'upgrade' issues. Bubblehead1980 was also working on his version, but we haven't seen his just yet. But, there is also a version of TMO / RSRDC that Bleiente did, called Ralles RealModPack., in which he includes some nice changes from TMO with RSRDC. Some aspects of the mod are too tough, other aspects are too easy, so we are working on a base 'balance' at this time, which is the one part of TMO that is 'set' - but that is also because it is not being tweaked on by its author.
It is based upon TMO v1.7, originally from the AOTD_MadMax team, and it has all of the ships planes and shore installations of Max's mods, but also quite a few assets of several other mods as well.
It is in 'production' (a fancy word for 'tinkering'), and we are about set to unleash the next version upon the SubSim community, hopefully within the next couple of weeks. Being biased as I am, I'd vote for Fall of the Rising Sun Ultimate as the best overall.