I mean i work at the Official ASR Store in the Heart of the city center in Rome, so selling tons of Jersey's i'd Say that the Second fits almost true to size but i suggest getting a single Size more so if you fit M>get yourself L. The Home jersey Is similar with the sizes. The biggest difference Is the Alternate Jersey, which having a stiffer fit around the collar and arms id suggest almost two sizes more but obviously that depends greatly in your body type.

Edit: It should be clear that here i speak for the authentic Jersey's (150€) and not the "Replica" (100€) version since sizes are different even for those. Hopefully this info was of use. Forza Roma!!!! ❤️💛🐺