If I recall, a common mistake I see is improper setup for exchange. I am pretty sure (cue Tracy Morgan commercial) that the proper setup is for the exchange data buckets should be on a direct attached lun to the host/vm. It can be fibre channel or iSCSI.
i see customers making using a lun attached to the ESXi host and putting a vmdk for exchange there. Although it works, I think I read in the SnpCenter docs that the configuration is not supported
SMBR is a very good product. I have used it to restore emails items/mailbox. For database restore, you can use the SnapCenter for Exchange product. As far as snapshots are concerned, I believe it should be whatever supported by respective ontap versions:
In ONTAP 9.3 and earlier, a volume can contain up to 255 Snapshot copies. In ONTAP 9.4 and later, a volume can contain up to 1023 Snapshot copies. Snapshots have no bearing on the exchange server performance.