For the next step, I would like to have it more organic. The ends of the branches can be a bit longer, at the same time the stroke strengths should be a bit more irregular. I’m thinking of something like this, but it doesn’t have to be so extreme:
This can be done to a certain degree with the Multipipe component. The NodeSize and SizePoints inputs are key here, which let you define for instance random thicknesses (or radii) at different points along the input curves. This also works with the legacy Fatten component (cf. R).
Have you tried playing with the R- and R+ inputs of the Prox component? These should let you play with different configurations. Instead of grouping 5 close nodes, you can also dial this down to get longer spanning segments.
In you reference image there are two structures that are kind of interwoven, which could also yield a need effect, but could be harder to setup.
This approach to produce varying thicknesses has a problem with self-intersections. These are kind of hard to deal with, but you should find a couple of configurations without any by playing with the random point seed and the other parameters.