I have the nightgown ordered in size XXXL, although I rather XL or XXL wear, and that was the right decision. The nightgown is namely not potato baggy cut loose, but rather "just". It order 1-2 sizes larger, providing the certain freedom growth)
The fabric of the nightgown feels good, I could not say that I would sweat amplified therein - on the contrary I have the impression that the substance is likely quite breathable.
Is definitely not my last night shirt for men!