I did not try ist myself until now. But from the docs it should be possible to call WL from other languages and vice versa.

But this is not my current problem. I would be happy to know from others experience which Wolfram environment is suitable for developing large projects with pure WL.

Great, Mark, thank you very much for explaining things.

This helped me a little. I am happy that I am not the only one classical developer who is confused by Wolfram's product structure. (Sometimes I thought I am too old (66) and meanwhile too stupid to understand that :-) )

But the question remains: Which of the many environments would be feasible to develop large projects? Programming Lab is definitely not a solution, since it has no idea of "projects" or the like. There are just stand-alone notebooks - maybe linked by manual hyperlinks. If I imagine to develop and deploy some large project with some millions of lines of code, some hundreds of files and some tens of developers and domain-specialists and all their domain-specific reports: It would be a nightmare.

Anyway: Fortunately I am no longer in this kind of business. I am now working with Wolfram just for fun. With pretty tricky algorithmic/mathematical problems, but no more with huge real-world-projects. This kind of things can be solved within some large WL-notebook.