Hi,
7 mode cannot do SMB3, Both Windows 10 and 7 can use SMB2.1.
Are both Windows 10 and Windows 7 in same subnets ?
Is the issue seen only when initial opening of the share post mapping or connecting to it or slowness is seen when traversing to every subfolder?
Since this is a performance issue, it is best to gather a packet trace and perfstats and open a ticket with Support. Support will be able to look at the logs and can help identify the problem.
So I would suggest to open a new support ticket for this issue.
Also ONTAP 8.1.4 is an old code and is EOSL as well as EOVS. So i would also recommened to upgrade the ONTAP code to the latest and supported ONTAP version 8.2.5Px.
Thanks
Vijay