I'm a military fan who picked up 3D modelling as a hobby, not a professional modeller so there are constraints to my work, most which a highly irregular release schedule and the limitation of scales at 1/1200 or smaller.
Barrels on Painted Samples:
Barrels on 1/1800 Painted Samples are added via tapping a hole and inserting a 0.3mm wire. Models are printed without barrels due to printability limitation.
Waterline subs are explicitly modelled at mid-hull instead of their real waterlines to maintain printability and to show the hull shapes. Different modellers resolve this issue differently.
Practically subs can be scaled as big as 1/350 and surface ships 1/700, and down to a scale of 1/6000, otherwise limited by printability. Please note that some Models can only be printed with Hi-Def materials. (FUD,HDA)
These are modelled specifically for Carrier models, and they are only likely to be available in 1/1800 and maybe 1/2400. This restriction reflects the printability limit (for smaller scales) and the time it takes to make better detailed aircarfts (for largers scales).