I have tried everything imaginable to resolve the keyboard lag issue. I do want to tell you that it is intermittent. For example, I have accessed this site page via Chrome and while typing, I have found it to be smooth so far. However, in other websites in Chrome or Firefox (which I have to use for work purposes), the lag is simply unbearable since characters are dropped and normal text converts to meaningless garbage that requires constant manual editing and correction (by the way, the lag has begun again while typing this).
I re-installed Windows 10 last night (this machine was Windows 7 bundle originally), checked all drivers for keyboard and elsewhere, updated browsers and cleared caches. Despite all of this, the keyboard lag continues. Anything else to try?