Okay let's go over this hand.
If we first think about what would be an optimal play, then checking first would be fine in my opinion. Betting quite frequently but very small is another fine option. I checked this also with Snowie and the result is the same. It would mix checks and bets with 25% sizing, but it would bet more frequently than check.
Then OTT because we went with this line and have one of the strongest hands, turn opened FD for some backdoors that might have stabbed. I think it is just a super clear call on this dryish board with TPTK when villain bets totally standard sizings. Snowie agrees and it is not even close, it is so clear call as it can be.
OTR I initially said that I would be tempted to call, so would Snowie. It would call something like 80% of the time, but because it would sometimes fold it means the EV of calling is 0 or very close to it.
So against a competent villain I think this is played quite well.
My reasoning to check call OTF would be that our hand is not vulnerable, villain can't have much and we might not be able to extract 3 streets of value anyway. Starting with a check could make it a bit easier for us to play because we are OOP. The reason to call OTT is simply because we have TPTK which is quite strong on this board and villain can be barreling many hands that we beat. Clear call imo there. And river is whatever as said many times before.
1. NL20 - tendency in this field: 'typical unknown' villains would call a lot of weaker hands (all Qx and middle pairs) for 2 or even 3 streets... Some of these hands he will check-back and fold OTT 6x, 88-TT on J, K, or A..
Typical unknown, if he is any good, will not even have many Qx hands here. Middle pairs he can call OTF but I really doubt he is going to call 2 streets with many of them and getting value from those on 3 streets is too optimistic. I disagree about that he would check back with some of those and then fold OTT. If he would call one bet OTF then he probably is more likely to call the turn if flop is checked. For example now the board didn't get very scary but opened some maybe possible draws. If the flop would have been checked through and we take a stab OTT, it looks just like it, taking a stab with a weak hand. And according to my analysis a typical unknown probably folds slightly too much against cbets so that it quite the opposite of getting 3 streets of value from 77.
2. It's much easier to play this line against unknown and not to commit ourselves in tough spots (just like TS posted...) : we have initiative+ info if he raises, we don't give him reason to bluff much by showing weakness etc.
I also disagree that it is easier to play. I would say check calling once, twice, three times is easier than betting and not getting any info and then maybe checking or betting small OTR and not know what to do when villain either bets or minraises us there. We get some info if he raises but really can we just directly fold TPTK on a dry board if the raise is not huge? Also we don't get any info if we just do the betting. Also we are not showing weakness. Good villain at this limit doesn't automatically think we are weak when we check a flop like this. Also what does it matter if we look weak and villain start barreling, our hand is often good here so it shouldn't be a problem.
And why did we call on the turn? We call turn for what proposes? Do we stand good enough with our hand? If we have a reason to call turn, than what have changed on river? How many backdoor flushdraw in his range? I mean, that we behind on turn or flipping against combodraw, but what is our plan on most rivercards? Just call 80 % pot on turn to fold a river? How often do you see 2 barrels of such sizing and check on river?
We call OTT because we have TPTK and the board is not very scary. Villain could easily be double barreling some weaker Qx or good pair like TT,99, he can also be double barreling some drawing hands. So yes, I absolutely think we are still often good enough with TPTK on this board that we should call an 80% pot bet. Absolutely. Now what changed OTR is that the possible backdoor flush did hit, something like A♣:T♣:, A♣:2♣:, A♣:4♣: and so on would be somewhat reasonable in his range. And also he bets huge. And as said above many times, I don't think calling that river shove would be terrible. I'm not sure why you don't think calling the turn is ok. Are you result oriented because you saw how this hand ended? I think there is a smaller chance that river improves villains possible bluffs than it doesn't.
So my plan on most of the river cards would really be to call a reasonably sized bet again. It happens quite often that villains bluffs get out of hand and he is just barreling like hell when he has air and we check to him OTF. And how often I see double barrels with standard sizings and they slow down OTR? Very very often.
, 9, T, K is bad run for as, and our 3 outs to A aren't as good also - he could play KTs like this... 
But in this situation we just can play max exploiting game and it will be more profitable... 
