In my specific case, TG drives my Graphics card bonkers. So I cant have TG open and do to much of anything else without getting "crazy screen".
So I learned from that to turn things off. I don't really know how much time it shaves off by having other programs stopped. But I know it saves a lot of frustration. And whatever time it saves, its at least clear that on my system some time is being saved, since you can visually see TG slow to a crawl when Im doing other thing while rendering.
Although, I don't reduce the amount of resources TG can use even for browsing. I figure I cant changes things mid render so there is no reason to reduce power for TG just to look on line for an hour during a long render. (threads, cores)