So, I always had this problem with my PC where my mouse latency felt different every time I restarted my PC. It felt like velocity was added to my mouse every time I moved it and at random values. I tried lots of different things and nothing seemed to help me. This kind of problem is also hard to troubleshoot since it's sometimes really hard to detect if it's fixed or not unless you play a game for a bit. This made me lose a lot of Overwatch games :(
When moving your mouse instantly from one side to another, you can see the delay. It should be INSTANT, but it is not.
• New Mouse
• Different USB Port
• Interrupt Affinity Policy Tool
• ISLC