TXAA is a (normally) slightly less demanding form of anti-aliasing than MSAA (that you mentioned using in your first post), with TXAA 2x being naturally less demanding that TXAA 4x. If having it turned on only 'costs' you 4 FPS, then good for you. If you do want a cheaper, less demanding form of AA, then SMAA or temporal SMAA would be the way to go.
When it says the 770 'features TXAA technology', all it means is that it supports it; it's an nVidia only technology, and can't be used by AMD graphics cards.
Unless you're running your fan at 100% all the time, it's unlikely to fail on you anytime soon (extremely unlikely within the warranty period). Increasing it slightly to lower temperatures at high load, if that's what you desire, isn't going to make much of, if any, change to the fans longevity. You don't need to increase the fan though, your temperatures are still pretty good as is.