In the case of wound bass strings, generalities don’t help much. As the tension on the solid string, or in wound strings, the core string, approaches the breaking tension of the string, the inharmonicity decreases.
So, for example, lowering the pitch of a harpsichord from A440 to A415 will increase the inharmonicity-how much, I don’t know. That will depend on the % of breaking tension of various strings at those pitches.
That is also why the highest brass string in the bass sounds so clean and breaks so easily.
A problem with wound bass strings is that the core wire %s of breaking tension become skewed irregularly, producing a warped network of higher partials. In the low bass of the piano we hear very little, often none , yes, NONE of the sound of the first partials. The low sound we hear, if we hear anything, is an auditory system response to the higher partials. In wound piano bass strings designed with up-to-date scaling programs we can hear a clear half step progression all the way down to A0, but, again, it is not the fundamental we hear, but rather a response to the well-designed overtones of the strings.
Stephan Paullelo offers piano wire in a variety of breaking strengths. When the % of breaking tensions of each note are controlled as part of the scale design the piano tunes more smoothly and small pianos take on the inharmonicity curves of larger pianos.
Simplifying: the problem of inharmonicity in bass strings lies not with the fundamental of the string, but with how well, or poorly, the partials of the low string can match with partials of the mid-range notes that are so often played harmonically with the low bass notes. Getting beyond tuning theory, it may be worthwhile to look at the “big” concordances of the music we are playing, at the octaves, double octaves and 12ths in significant progressions that show harmonic beauty (whatever that means to you). These harmonies can be tested as the conclusion of whatever tuning method is used, and corrections can be considered if needed.
It’s probably worth learning to hear the multiple coincident partials involved in perfect intervals, as this is where irregularities of scaling will be audible.
Compared to piano tuning, harpsichord tuning is a very straightforward endeavor. Harpsichords are naturally wonderful. Pianos are overloaded contraptions. I am so glad to be a RETIRED piano technician. Whew!