I'd give the a thumbs up to smart_open. Happily used it to have our servers parse data dumps of up to several hundred megabytes on user-configurable remote storage without drama. Seems like it could handle larger files without issue, but we haven't had need to push it.

I can't speak to fsspec, but their filesystem functionality (eg. `ls`, `cp`) isn't something that smart_open has and it does look cool.