have you tried using mods, there is one that speeds up the animations maybe that will fix what ever strange lag you have. Instant actions mod.

I have a very similar system, but based on an i9.

For some reason I do not understand, having a browser open at the same time gives me a slight stutter, especially when kicking. No graphics setting seem to have helped. Having just MT@P running, disconnecting from the router, and disabling firewall, anti-virus and anti-malware got rid of most of the problem.

I think it's probably a Win10 issue. My Win7, i7, 16g DDR3, 980 STRIX, without SSD runs it much better.

It's not your system it's the game engine itself, unity is notorious for bad game performance, and this game, while having very competent developers simply cannot overcome the limits of the engine as it has a small budget for detailed assets loading/unloading into the world areas...

While there may be a loud and emotional defense of the engine, the fact still remains that unity has limits to what it can accomplish before performance issues crop up... if this were a small game world and/or a 2D game or if it was developed on the unreal engine, there would be no issue.