External libraries? What do you mean by that? External storage?

The last time I looked, Immich can’t work with a existing file and folder structure without importing (copy) everything in his own structure (database). That’s a big no go for me.

In Memories, the file structure of your photos is preserved as-is. And you can run it alongside with other solutions that respect your folder structure.

EDIT: looks like Immich can work with external folders. But: Does it put pictures from my phone in that external folder or in its own folder?