> unlike Pascal-style strings, they can be usefully sliced, especially if you can modify them strtok-style.

Slicing Pascal-style strings is also easy and constant-time: just track the buffer, offset, and length of the slice of characters you want. Java used to do it implicitly whenever you called `substring`.

> unlike (ptr,len) "Modern C buffers"/Rust-style strings, references to them are pointer-sized, and they can be used as a serialization format.

Every C method that takes a character buffer either a) has a corresponding length parameter or b) is avoided because of the security risks. In practice this means that C also stores the length information, just on the side instead of combined into a struct with the buffer.