Searching for the best Solution to connect a NAS with an external hosted Nextcloud

Hello everybody,

in my current set up i have a Nextcloud hosted by myself on a NAS (as an LXC) and in their i have some SMB-Shares connected with the Nextcloud. Now i want to move the Nextcloud to an external Webhoster and i am searching for a good Solution to bind my NAS into it. I think SMB over the www isn’t a good idea. What do you think? SFTP or maybe WebDAV? How can i realize this securely?

Kind regards