Well, you can't 3-bet/fold TT. Its simply to strong of a hand to do so. By the time you get 4bet there's already 35-45BB in the pot and you always have some fold equity + 36% equity against QQ+/AK so folding TT preflop is a mistake. Your basically turning your hand into a bluff.
It not an easy fold to 4-bet preflop.
Why would you think your ahead of someone's range just because he only called your 3-bet or that his range is narrow? That makes least sense of all. Thats really player dependent and his 3-bet calling range. Most people flat 3-bets OOP with 99-JJ (KK and AA sometimes) and KQs AQo type of hands so your no way ahead of a tight calling range since your either flipping or crushed.
On the other hand some people hate folding to 3-bets and will call you with all types of Axs and SC in which you are way ahead of their range, but in this case their range isn't narrow at all and against them its profitable to 3-bet since you get more money into the pot against weaker hands.
By only flatting preflop you keep his range wider. He still has undercards in his range as well as lower PP which your crushing and most people fold those hands OOP against a 3-bet. You can also hit a set and stack him in case his got QQ+ or flop set over set since TT will usually be top set in which case you get to stack them.
The line you should take depends on board texture and the opponent. I usually C/f on AKQ type of boards.
