A question regarding HC

I just want to ask if the servers for SC and HC are different, and if playing in HC will reduce the lag/latency since less people play HC. Thanks

I am not sure, but what i noticed since i upgraded my PC i barely see any latency.

Not any more frequently than different instances of SC are on different servers.

You might be confusing the term "server". There's a central data server everyone uses in Texas, and there's local servers, and gateways... it's a lot more complex that it looks. Most latency issues aren't related to the game itself, but to how you connect to it. Depends on your location. Depends on your ISP.