Hi,
1. There is no best practice regarding datastores. I'm using 500gb, 1tb and even 2tb datastores with SRM. On some datastores I have 15 virtual machines and others just 1. When a VM is on multiple datastores, SRM will detect that en place them together. Its a good idea to place these vdisks in the same consist group.
Also mind the remote vdisk ID. When there are doubles SRM will detect them and show them as VMware datastores in de device view of the SRA. Huge bug.....But doenst seem to break the functionallity of SRM
2. On some disks we have change volume. Works fine. It's even supported by IBM
3. Please explain versioning (I'm not actually managing the SVC environment , just know the bits for SRM to work 
)