Q. What is hyperconverged?
A. Essentially "hyperconverged" means the compute and storage capacities are combined, for example in a Hyper-V environment the Hyper-V hosts also contain the storage used by the virtual machines. This can be enabled in clusters by having solutions such as Shared Storage Spaces using an external storage enclosure which is connected to the multiple hosts. In Windows Server 2016 this is enabled further with Storage Spaces Direct which enables the local disks in the nodes to be aggregated together into a Cluster Shared Volume which can then be used to store virtual machines, essentially a vSAN.
While hyperconvergence is very attractive for smaller deployments, it becomes less attractive as the scale increases beyond a few ten's of servers, because the compute and storage scale is tied together which may not meet the actual requirements. Perhaps more compute is needed than storage and it is at this point it is better to separate the compute and storage so each can be scaled independently to meet requirements. Technologies such as Storage Spaces Direct could still be leveraged however now those Cluster Shared Volumes would be used as the storage for Scale-out File Servers (SoFS) and that storage would be used by separate Hyper-V compute clusters that would access the storage via SMB.
The key point: Use whatever fits best for your organization.