It depends on you which Datastores will you present/add to which ESXi.

DRS, HA policies you can define on cluster level, so it is configurable for group of hosts.

sDRS is at the Datastore level. You can keep VMs on separated. You can keep VMDKs of the same VM together. You can do I/O latency thresholds, which you can also setup on a SDRS schedule. This is metric-based that isn't running ALL of the time.

Yes,

But remember that Storage DRS has same requirements.

https://docs.vmware.com/en/VMware-vSphere/6.7/com.vmware.vsphere.vcenterhost.doc/GUID-A16BA123-403C-4D13-A581-DC4062E11165.html

DRS is responsible for optimizing and balancing the usage of CPU / RAM resources in the cluster, But Storage DRS has this duty for datastores (VMFS / NFS) by consideration capacity and I/O metrics. DRS have affinity/anti-affinity rules for VM/Host but Storage DRS have rules for VM/VMDK files. They can work co-exist together, so there is no conflict about DRS & SDRS co-operation into the cluster. Actually, based on SDRS FAQ there is following important requirements of SDRS:

• VMware vSphere enterprise plus license. Also, it's recommended VMware vSphere compute/hosts cluster.
• Shared datastore volumes accessible by at least one ESXi host inside the cluster. VMware recommends to have full cluster connectivity, however, it is not enforced 
• Datastore inside the Storage DRS cluster must be visible in only one data center.