Fresh water and torpedo load
The Type XXI was fitted with the same water still of the Type IX. The plant however was not designed to be operated at snorkel depth and to do so would create all the sort of issues with piping, heat management and IIRC contamination of distillate by salt water during pressure drops caused by the snorkel valve shutting off. The XXI water needs, owing to the larger crew and more cells, were also greater than the IX; the XXI would thus have to rely largely on its water tanks. The postwar american reports note that at at US style consumption rates water would have lasted less than a couple of weeks. It could have been stretched further with conservation measures and, according to a source, by using trim tanks for extra storage but if you want to be realistic a prolonged stay in in tropical waters in 1944-1945 is probably not a good idea.
However, U-2511 destination before surrender was the Caribbean, whether the issue had yet to become apparent to BdU or it was deemed manageable for a short stay I cannot say.
The issue was fixable with a properly designed water still, whether the germans were working on that I have not been able to determine.
The XXI ws fitted with enough tubes and racks for 23 torpedoes, but three racks were left empty for moving and servicing the weapons.
There is a mod to simulate this that can be found in this
thread . No list of the actual types carried is know but it can be inferred that TIII Lut II would make up much of the load, with perhaps a smaller proportion of passive homing torpedoes (TXI likely) than that carried by conventional U-boats. FAT torpedoes would not be carried (mechanical incompatibility or so I have been told).
Advanced torpedoes were in the pipeline, though of those only the T VII is partially modeled in the game.