good question! I have always installed the primary and workers on the same corresponding drive (G:\Tableau\Tableau Server) and therefore I don't know if installing the workers on a different location would just confuse the cluster or not. It may work and it's worth testing.
In reference to your second question on High Availability, there are cluster controller and coordination services that are installed on every node, and they watch for failure of the data engine / repository processes and will failover as appropriate. And it keeps the two in sync via the file store process. there are multiple references to this topic. Here is one: Understanding High Availability