The MySQLi server behaviors extension is a starting point for us in moving the other extensions to use MySQLi.
We have upgraded cart 6 to also use MySQLi, and are currently working on an Upgrade to Data Bridge that we hope to release this quarter, then we will be working on Design Extender.
If you want to get familiar with the differences in MySQLi in advance of the other extension upgrades being available, the MySQLi server behaviors would be a good place to start.
as for upgrading the DW version, I Would move to DW Creative Cloud, it is a lot more stable than DW CS 6.