They are compatible as in pin compatible with regard to add on displays. So if a display works with RAMPS, it should work with MKS.
It's based on the same MEGA2560 microcontroller chip that is used with a RAMPS board so it should be able to run firmware RAMPS could: Repetier-Firmware, Marlin, Sprinter, etc. Any host software that can talk to the firmware should work: Repetier-Host, Pronterface, Octoprint, MatterControl, Simplify3D...
Most boards are going to be made/assembled in China so I'd just assume that a Chinese manufacturer would assemble their boards there too.
Can't comment on the quality or reliability of the board or components. It's priced about the same as what you'd pay for a RAMPS and MEGA board, and it's a cleaner solution since it's not in the format of a shield. It doesn't look like there's a schematic for it and that it's closed source, so there's a philosophical issue if such things concern you.
