If you want to determine the effects of latency locally, you can use tc netem on a linux box with two ethernet adapters and place it between the PC and the SMB fileserver.
Then you can adjust the latency via software.
You can also test how VPN affects “throughput” independently from the latency due to speed of light in a WAN.
See How to Add Latency for Testing?
Another reference for using tc to control latency, packet loss, and bandwidth