Hi.
According to the latest VSCAN TR's, sizing for vSCAN need to be done via the internal NetApp SPM tool.
https://spm.netapp.com/
On older releases of the TR's there was a sizing formula (I have no idea why it was remove, I'll give NetApp the benefit of doubt and say it was probably for a good reason - hence should not be used any more) :

As for your request. There's a Microsoft tool called FSCT to simulate real-world stress test on the file server. I never seen anyone using it with ONTAP (except for now - see below) and have no idea if this scenario supported by NetApp, McAfee or Microsoft. The tool along with DOCs is downloadable from here:
https://www.microsoft.com/en-us/download/details.aspx?id=55947
I now see it's been used by NetApp themselves to benchmark NetApp Files in Azure and AWS, and there's someone who tested it in ONTAP 7-mode. So I'd assume it will probably work....
https://cloud.netapp.com/blog/aws-windows-workload-performance-cloud-benchmark-test
https://cloud.netapp.com/cloud-volumes-service/azure-benchmarks
https://community.netapp.com/t5/ONTAP-Discussions/NetApp-FSCT-testing/td-p/3897