Sokolov's book is great, but quite advanced. I guess the best source for the Tartakower is still John Cox's book on Everyman. It's ten years old, but there are no great changes since then.
https://everymanchess.com/products/declining-the-queens-gambit
It's completely sound. I believe once you play bb7 there's possibilities of opening the bishop with dxc4 and then playing in Queen's Indian style with ne4 but I could be wrong
If black gets it wrong, white is going to play cxd5 and box the bishop in on b7 or get a big central attack. cxd5 is the standard and very effective counter to any defence where black plays b6.
You have to enter Bxf6 before that, else Black will simply take back with the knight and get a very comfortable position.
Yes, it's tricky, which is why I prefer it as black because a lot of people don't get the move order right as white. Whereas cd is an immediate response in many openings where b6 is played, I'm starting to try to time cd in many openings to where I can see a slight edge for white if N takes. Often, it's nothing more than a tempo gain I'm playing for or sometimes less than that ... just a better placement for a piece. That's often enough to get a more aggressive position as white.