No. None of the Realme models comes with earphone. Realme X standard box packaging includes Realme X mobile, USB Type C Cable, Power Adapter, SIM Ejector tool, Protective case, and a user guide.
Realme X has industrial-grade polycarbonate back panel.
Yes, Realme X does have a 3.5 mm headphone jack.
Yes, Realme X does have the Dolby ATMOS support. It is enabled by default.