Last year Xiaomi introduced its proprietary Surge C1 ISP chip bundled with the Mi Mix Fold and according to a leaked source code, the upcoming Mix 5 Pro will likely make use of the second generation Surge chip.
It's still unknown what kind of special features the Surge C2 will bring to the table and there's even a chance that the phone will arrive with the current Surge C1 ISP. What's for sure, the standard Mix 5 won't be getting the C2.
The report from Xiaomiui also goes into detail regarding the camera sensors of the two Mix 5 devices. The Pro is said to adopt a 50MP OIS-enabled main camera joined by a 48MP 5x telephoto and 48MP ultrawide camera. Whereas the non-Pro will settle for a slightly less wide 48MP ultrawide camera and a 2x telephoto unit, still 48MP, though. The interesting bit is that the Pro model is rumored to offer a 48MP front camera as well.
The Mix 5 series is expected to make a debut in Q2 this year, but don't get your hopes up because it will most likely remain a China exclusive.