it's interesting tho, that there seems to be much tempi concensi on how these pieces are played. I google recordings to get a gyst and to hear how pianists interpret Bach's works. They are NOT all over the board.
On the other hand, if you check the appendix "Table of Tempo Indications" in Willard A. Palmer's Edition (Alfred Masterworks) of the WTC, Bk I, you'll see that tempi are, indeed, "all over the board."
Just a few examples among pianists (not including harpsichordists, here, although there is a listing of tempi taken by the latter) such as Demus, Fishcer, Gould, Gulda, Martins, Richter and Tureck :
Prelude No 1 : from 52 to 96 per quarter
Prelude No 2 : from 63 to 132 per quarter
Prelude No 8 : from 52 to 80 per quarter
Prelude No 16 : from 72 to 102 per eighth
Prelude No 23 : from 63 to 96 per quarter
Fugue No 2 : from 60 to 88 per quarter
Fugue No 7 : from 76 to 104 per quarter
Fugue No 12 : from 40 to 72 per quarter
Fugue No 21 : from 69 to 112 per quarter
Fugue No 24 : from 30 to 80 per quarter
Palmer makes similar tempo comparisons in his edition of the Two-Part Inventions where the same wide range of tempi can be observed :
Invention No 1 from 60 to 120 per quarter
Invention No 6 from 80 to 120 per eighth
Invention No 9 from 40 to 80 per quarter
Invention No 13 from 66 to 144 per quarter
Invention No 15 from 54 to 104 per quarter
These are pretty wide extremes, it seems to me, and many of the other Preludes and Fugues and Inventions exhibit the same wide range of tempi.