I've always been diappointed in Darwin's writing on architecture. Compared to Darwin's contemporaries (Hunter, Thomas, CBM, and MacK) he doesn't seem to have much to say about architecture, per se. He talks a lot about courses, less about design.
Darwin could write circles around those guys, but they were a lot more focused than he was on architecture.
Darwin's best stuff, imho, is when he is thinking out loud about the travails of playing the game, competing against friends and the frustrations of hitting a golf ball. These are "essais" in the spirit of Montaigne's Essais. There is a remarkable candor about them. They are the pieces I come back to.
That stuff is magical, but the rest of Darwin has not aged very well for me.
I want to read his bio of James Braid. I've heard it is very good.
Bob