Pogonina vs Chess.com Move 20. ...
I will be out of town for a day or two, so I will not be able to comment much on Pogonina's move 20 and our response to that. I will try but there is no promise.
Move 20 is interesting though. Black's main problems are the passive pieces Be7 and Rf8 plus the weak pawns on b7 and d6. Any Black plans would have to deal with those issues. Since Black's forces are tied down to those defensive points, or exchange options, we might be seeing further pressure from White and/or an alteration of the pawn structure on White's king wing.
Candidates after 19. ... Qc6. Not necessarily in any order of strength.
a5 Putting more pressure on our weak spots. Frees Ra1 from it's defence. any b-pawn moves in the future will result in an isolated a-pawn. I also liked b7-b6 in many variants, to stop a5, get rid of the weak square and lend a support to Nc5. All that is impossible then.
c3 Not really necessary yet and committing, so any piece route is no longer possible via c3.
Qb4 (Alenka) Avoiding Nc5, restricting d6-d5.
Rad1 Overprotecting d5, entering the half open d-line, defence of a4 is lost.
Red1 Overprotecting d5, entering the half open d-line. The e-rook isn't really doing a lot so putting it to work is good. If Black plays Nc5 Qd5 QxQ and RxQ and there is still pressure on d5. Pogonina might go Qc4 on Nc5, though.
g3/h3 g3 is prolonging the diagonal for Bf3 so it can go back. I'ts slow though.
In conclusion, even though nothing here is very deep, I see a5 and Red1 as the main candidates. The truly best positional move I think is 20.a5.
Alright, she went for my second best choice. White is decided to not loose control of the d-line and the centre. A very sound move. It leaves Black with the interesting choice b6, now or later. Anyway, not having much time on my hand, I see no reason not to play 20. ... Nc5.
20. ... Nc5 looks like the the most natural and best move. I think 20. ... Rc7 is a small mistake, it doesn't obstruct the buildup against d5/d6. True, 20. ... Rc7 threatens 21. ... Qxc2 but that is easily met with 21.c3, which is an ok move for White anyway. Alenka's 20. ... h6 is a very good move. Sadly unseen by many voters