First go at a response: still pushed for time. Retired long ago and seem to spend all my time in Zoom meetings! Listened to your excerpts: good that you are experimenting with different touches. Whatever I write is opinion only: I do not set myself up as an expert or a teacher. You may already know much, if not all, of what I write.
One of the beauties of the harpsichord is that much of the part writing reveals itself in that having different dynamics as on the piano is not possible so other means are necessary and lo and behold, that inner part is clear. So inner parts etc will be heard when we use the appropriate touch - staccato, legato etc - and also articulation. Whereas on the piano we can accent a note dynamically, on the harpsichord we can slightly lengthen it: flexibility of rhythm is important without it appearing to be flexible in romantic music terms. So leaning into a note and holding it fractionally longer gives it slightly more weight/impertance. Staccato, legato and all shades in between are key elements in providing musicality, as is phrasing. With no sustain pedal and a smaller degree of resonance than the piano, the ends of phrases can become clearer more easily and a crisp attack/release fits the nature of the instrument. One useful rule of thumb, especially in the bass, is to play notes separated by a tone or semitone legato (within a phrase) and longer intervals more detached. It often adds interest to what can seem to be a relentless passage of notes with not much obvious musical interest. A good first step in working out touch/articulation/phrasing. (Handel - even though I prefer JSB - has fabulous bass lines. Listen to good renditions of the concerti grossi)
Before I forget: use of different registers. Yes, a change of colour makes it easier to differentiate between, say, the sections of French rondeaux, but the real art of realising baroque music on the harpsichord is creating changes of colour by touch, articulation and phrasing, plus another dimension beyond that of creating "accents" by slight lengthening of a note. This the "sprung rhythm" of the baroque period. Listen to John Eliot Gardiner in Bach cantatas/passions. We can do the same on the harpsichords, indeed need to in order to give the music life.
Instrument: Pianoteq has a number of good to excellent instruments, certainly in comparison to the built in sounds of a dp. The two best, in my opinion, are the Hans Ruckers II and the Giuisti. Different: the Giusti has probably the more authentic sound of its type, somewhat dark, the Ruckers the greater flexibility in registration. Experiment with both in demo mode - assuming having both is not possible or desirable - and choose for yourself which suits you best. We have to accommodate as best we can to the action of a dp, which is very different to that of an acoustic harpsichord.
The real art of playing the harpsichord - more so than applies to the piano - lies with being unable to detect quite how the experts create the musicality, the life of the music, in comparison to our somewhat plodding efforts. It is very subtle.
Just some thoughts. There is also, amongst other aspects, the world of different cultures: French, Italian, German styles and how they changed over the timescale of plucked keyboard instruments. Hope this is helpful.
