According to the site Faq:
It is not emulated, they are using one single chip for the 16Bit and 8 Bit processors.
Compatible with original cartridge ( with few exceptions like Virtua Racing and Sonic & Knuckles ) and original controllers
They are keeping the original design, even the box will be based on the original.
No promises about compatibility with Game Genie, Sega CD, Power Base Converter, 32x Meganet, Activator, e Mega Mouse