For the core of my engine, I just need to build some basic mesh tools like mesh(), combine(), intersect(), difference(). Everything else, common objects like cube(), sphere(), disk() and common operations like move() and rotate() is then simple.
SolidPython: This seems to rely on OpenScad. I think a solution without dependencies will fare better in the long run.
PythonSCAD: This also seems to be heavily interwoven with OpenScad.
CadQuery: This might be interesting. I will probably start with some code for mesh(), combine(), intersect(), difference() that I write myself and then look into libraries like this one and evaluate if it makes sense to swap out my own for one of them. But I have the feeling they will not match my preferred architecture closely enough.
What do you mean by "Due to the large size, python really isn't suitable for embedding in wasm"? In what regard is Python "big"?