I can listen to a harpsichord for an hour or two but after a certain point it starts to wear on my ears in a way in which a modern piano does not.
I am also in the group who firmly believes any of the old composers if given a chance would far prefer a modern piano as well. When the Fortepiano came out they ditched the harpsichord and began writing for the new instrument. To me they were very forward thinking people and especially Bach himself was arranging his own works for different instruments so I don't feel he would have had any issue with it.
I do occasionally delve into harpsichord music for a while but I much prefer to listen to a modern piano, especially for long stretches.
Richter is my go to for the WTC on the piano. He is miraculous. Lush and full. The piano in bloom. And yet every line is clear, and bell-like.
Scarlatti Sonatas probably. But then again I'm spoiled listening to the magician, Vladimir Horowitz.
As a matter of fact, I just ordered Horowitz playing 20 Scarlatti Sonatas because I can't find anything by Horowitz/Scarlatti in my house. When I moved, it seems some of my stuff got lost.
Maybe Scarlatti/Horowitz is somewhere up in the attic along with the Mahler Violin Concerto.