Cool! Totally confirm my tests! :)
They are all tangent, centers are very near the Orange curve sometime up, sometime down...
Seems very sufficient for graphic drawing

And super the trick to use Flow for Bending something!

Now wait and see the little script or other trick for automate that! :)

In my opinion maybe more easy for the user to Put "first" and "last" circle with their own proportions sizes on the curve
even only the first one!

That gives the way of increase decrease...

And I would add that it's normal to have a difference since the inner and outer curve won't be anymore identical in length since they are at a distance from the reference curve and will be submitted to relative outer(enlarged) and inner(shrinked) distorsion.

Michel

The circle tangent command relies on picked points to determine which particular circle to make, in many situations there are multiple possible tangent circles.

But because it uses picked points it is not easy to automate this particular command unfortunately.

An automated one would probably need its own custom solver.

- Michael

So maybe a Scale Array of circles can make a cool approximation in just change the actual method of regular increase/ decrease ?
Mixed with the Array on Curve in just change the actual method of regular propagation...(same coef) here 0,7 for my first example

We draw only the 2 first tangent circles for calculate this coef !
Seems it's not a too difficult changement of the existing methods! :)

Using some simple trigonometry:
If theta is half of the angle between the two tangent lines, then the scale between adjoining radii for shrinking circles, is = (1-sin(theta)) / (1 + sin(theta)).
For the next largest circle, the formula is the reciprocal.

There are also Steiner chains, Pappus chains, and Ford circles.
- Brian

Using sine of the angle to calculate the location of the first radius did cause some rounding, like a radius of 10 going to 9.999999... or so, which I did not care for :-)