i know the opening to be an inferior version of the exchange variation of the queen's gambit declined. the reason is the nf3 allows black time to get the queen's bishop out to f5 or g4 which he normally can't do in the main line.
to your first question, in these lines in the queen's gambit declined, normally black would rather wait for bg5 and then ask white with h6, instead of preventing bg5 altogether. i don't know the exact reason why. i do know that the bishop on g5, while it looks great, can allow some ideas for black later, like be7 and later ne4 offering exchanges, or similarly, be7 and nh5 with the same concept, exchanging some pieces and freeing black's position.
to your second, i know that bd6 is possible even when nf6 is pinned, but it is hard for me to make it work and see it through, so i'd rather not play bd6 too soon. basically you have to defend d5 first, with c6, and then make sure that you don't get hit with the e4 break since your knight is pinned, and also that ne5 and f2-f4 ideas can be adequately met. with the bishop on e7 none of these ideas work as well.
to your third, i know yusupov to be an expert in qgd lines. the classical ones. i think also kasparov has some nice games with black in this specific line, the exchange variation of the qgd. i can't answer what kind of strategy since i never really delved into the intricacies of the line. i just know some typical plans for both sides but not necessarily gm-level intricate opening prep.
So I played h6 here and the game report thought both h6 and a3 were the best moves. What I'm wondering is, should I always prevent pins in similar structures? What determines the placement of my dark squared bishop? Should I ever play Bd6 if my kingside knight can be pinned? What kind of strategy would a GM or high level player employ?