Cerebrum123
Terrarian
This is a Steam issue, not a Terraria issue. You'd likely have the same result with any Steam game you tried to play under those conditions.
I know you've mentioned this a couple of times before - it's likely a performance issue with your hardware.
I see that you made a Tech Support thread here quite some time ago - I suggest that we revive that discussion there. My system's specs seem quite similar to the ones you stated there, and I'm getting consistent 60 FPS with no video or mouse lag. It's quite difficult to troubleshoot a single person issue in a general feedback thread.
I noticed that in this update I'm getting around 48 FPS, and my specs are pretty decent. I can get between 45 to 60 FPS on Shadow of Mordor. I have Windows 10, GTX 660 ti, 9 GB of RAM, and an i7 processor(always forget which one). That should be way more than enough to play this game at a full 60 FPS.