Fletcher’s integration with CeTZ currently sucks, but I’m working on it.
It’s being rewritten to be more like CeTZ, so you will soon be able to use cetz.draw commands directly in a fletcher diagram(), and conversely use fletcher nodes and edges directly in a CeTZ canvas(). The render option will vanish completely.
You’ll also be able to style nodes and edges with cetz.draw.set-style(..) like other CeTZ objects.
Fletcher will basically be a layer on top of CeTZ which gives you more powerful arrow styles and optionally lets you use tabular layouts for convenience.