I just bought the X9-S The New 2018 128bit 16GB Version with 5.1" screen, Firmware version 188.8.131.52301 (If i reading this right that looks like 2012?).
And it has issues, GB/GBC and NES all run great, GBA runs great but after 4 to 10 minute has some sound issues (cracking and sounds like an underwater tin can), Megadrive is 50/50 some games run ok others are to slow and jerky, now here is the strange one, SNES is running way to fast, Like about 40% faster which makes some game unplayable, CPS 1 Games run ok, Neo Geo bios/Logo screen is running really slow, but games seem to play ok, some do have slower music audio playback.
Menu is a rip-off of the PS-Vita, Lots of round icons and it scrolls up and down 3 screens.
Also when charging light flashes blue/red and never stops, i had it charging for just over 10 hours and it was still flashing, have tested with different chargers and USB Cables still the same so i guess that's just how it is.
I hope at some point someone will make a 5 to 6" handheld that will work great with all emulators (I can Dream), So GCW Zero is still the best handheld i have just wish it had a bigger screen.