My background is more on the singing side, and I absolutely adore his choral work (along with Haydn et. al). Over the years my voice slid down rather than went for a hard break, before finally settling in to a lyric bass-baritone range, so I've had the opportunity to sing pretty much every part over the years.

There's a long running joke amongst Altos that you can tell when the composer's wife was an alto, because you get melodic lines. Bach's choral work tends to include as much intricacy as his instrumental work, across all four parts. Bass still tends to get the "walking the root notes of the chords", but not to the same degree as with other composers.

BWV232, Bach's Mass in B Minor is a favourite of mine: https://www.youtube.com/watch?v=VY1w3EhXqwo