To BWV 860:
Prelude:
Indeed, that´s may be one of the most difficult prelude of WTC, I agree to your opinion you told above.
Overall a nice and even performance. You have choosen a good tempo, not too fast, not too slow IMO. And I think, it´s nearly the same tempo I have choosen in my recording. As always I have some little things to nitpick:
In the first part there are some missing respective inaudible single notes. I think you know yourself where they are. (You are the one with the elephant ears, not me.

) The end is better, especially the (quite tricky) bars 13-15 come out really good.
At the beginning you don´t play the breaks of eights (Orgelpunkt g), but that´s a decision of interpretation, I personally like it.
Fugue:
nice version. My only nitpick is, that you loose a little bit tempo in bar 10, but that´s minor, or was it an interpretative decision? Could I hear some voicing of the subject in the middle voices here? I´m not sure, because as usual you don´t too much voicing here, but that´s your manner to interprete Bachs fugues. As I said, I´m not the one with the elephant ears here, but to me this version seems to be note-perfect. Congratulations to that.
The tempo is a possible choice. (My version is slower, but I know, I´m a bit beyond the "mainstream" with that, of course, with fully intention.)
To BWV 861:
Prelude:
I really enjoyed that version. Nice calmness and capture of the mood. I like your use of the pedal here.
Fugue:
Also a very nice version, contemplative, very even and with tender approaches to voicings of the subject.
To BWV 884:
Prelude:
Wow, that´s a good version! The tempo and also some other things you do are very close to what I had in mind for my re-recording of that prelude. Very nice and artistic differenciation between first time and repeat of each part. Could be there is a little slip in bar 32 in the repeat, but that´s only a small nag as usual.
Fugue:
Again wow, that´s a version I will listen more than twice. I´m enthused. Nice agogic and interpretation. I like that slower version a lot, though my own recording is faster. (Seems that we did it just reverse in comparation with the fugue in g-major of WTC I, here I have choosen the slower and you the faster version.) Interesting execution of the trill in bar 52, I think, I will adapt that for me. In bar 62, 63 I´m not sure, what is wrong here: is it just the rhythm of the upbeat-run in bar 62 or is there really missing a note? I couldn´t fiddle that out, though I have listened to that passage three times. (Seems that the devil really always is in detail...

)But in every case this is a minor matter.
To BWV 885:
Prelude:
That´s a proper version. I remember that piece very well, because I have played it during a piano competetion in the late 80th. So I´m sure, there must exist an old recording of that time (unfortunately the quality of the cassette-tapes has decreased so much). I also remember, that I have played this prelude in the manner of a French Ouverture, that means consequently with a double dotted rhythm. You don´t do this here. And I have done more with the tension of chords and voicings. But apart from that it´s a good and decent version IMHO.
Fugue:
Also a very decent version in a quite high tempo. As usual I do more with voicing than you, but that doesn´t decrease the worth of your interpretation, that´s your personal style, and we all have the right to have this. With the usual advice to my non-elephant-ears I can say, that this must be a note-perfect version.
You have given me much homework today, but it was a pleasure and very interesting and inspiring comparation. I feel motivated now to re-record the g-major-prelude and step to g-minor. Fortunately there are Easter-holidays now (of course, with the usual amount of work, but also with more time for music).
Have my sincere congratulations to this great achievement, dear friend!