Welcome to SG.
If you've already optimized your connection with the TCP Optimizer, you've done most of the work already. There is no way to set the RWIN value manually in Windows 10. You can only set how aggressively it is allocated by the "auto-tuning" algorithm, and the Optimizer already does that.
You can look at some of the Gaming tweaks on the site to tune your wireless/network adapter locally: http://www.speedguide.net/articles/gaming-tweaks-5812