The PS4 has a more powerful PS2 emulator thanks to the “PS2 Classics Emulator” from the PS Store. Running a Tekken 5 PKG on PS4 offers upscaled resolution (1080p or 4K), smoother textures, and trophy support if you compile your own PKG.
For enthusiasts using custom firmware (CFW) or homebrew tools, the PKG format is the standard for installing game backups and digital software on the PS3. Tekken 5 Pkg
Historically, Sony used PKG files for the PlayStation Network (PSN). When you download a digital game, a PS1 Classic, or a DLC pack on a PlayStation 3, PlayStation Vita, or PSP, the system downloads a PKG file and unpacks it onto the hard drive. The PS4 has a more powerful PS2 emulator