That much is obvious. Your social credit score will be tied to your UBI. Bad score = low to no UBI, denial of all services, possible detainment for re-education, etc. Which is why it's better to GTFO off cities while you can.
Discussion
But there you have a two book system. One is monitored and the other not.
Sure, but it still leads to issues of trust for the black book stuff, since CBDCs are designed to be "burnrd" leading to a destruction of any value transacted coinage. That CAN'T work between low-trust parties.