Is Cryptomator a safe replacement for Veracrypt, durability- and performance-wise?

No. It is not meant to be.

As already pointed out by you and in your linked post, Cryptomator targets cloud storage encryption and is optimized for this use case. As such, there are trade-offs, such as leaking the last modification date of files (otherwise your sync client would have a hard time).

Veracrypt on the other hand doesn’t need to deal with 3rd party tools accessing the ciphertext, therefore it can layout data in an internal, optimized format and can protect more metadata. That’s why we recommend Veracrypt for local disk encryption.

That said, it is rather pointless to have your node_modules in a vault. In general, dependency caches only contain public data anyway (unless you work with private npm repos).