last time I checked large ( > 2GB) file upload using resumable is supported only for logged users. So I guess your suggestion will not work.
If I use php webDav client then the file must be first uploaded to webserver and only then to Nextcloud. It would be easier if TUS can handle even upload to Nextcloud.
You could just upload the file via TUS to a local folder, and then use the external storage feature in Nextcloud to access this folder (or SFTP, …).
Nextcloud provides webdav interface to transfer files. Webdav is not Nextcloud specific, for that reason you might already find implementations.
To have it work with Nextcloud, the best way to have such a thing as an app directly within Nextcloud. There have been upload tools, but they were discontinued… (e.g. Flow Upload - Apps - App Store - Nextcloud)