A question about options

I have used NC a little in the past as it is intended but have a question for experienced users.

A friend is looking for a solution and I am not sure whether NC is the best or maybe NC plus some Plugin.

They basically want to free up space on a phone by putting data on NC. This would then also mean the data is available on the laptop or any device with the same login credentials.

But can we get data ‘Off’ the phone without deleting it and have it available as ‘Thumbnails’ or an available folder or similar concept to browse when desired?

I’m concerned we will end up accidentally deleting data.
Am I going about this all wrong?
Any suggestions would be welcome.

Oh, I will be using a Raspberry Pi with SSD for data.

On iPhone, you can upload images to Nextcloud automatically (always or just over wifi). But I haven’t seen an option to delete them on the local storage afterwards. If you do it manually, you can browse through the pictures on the mobile app. There is nothing automatic of uploading them and replacing locally by a low-resolution thumbnail.

I am not sure about the Android app, they can certainly upload pictures.

Since some versions you do not need to download the file to see the photo from the android app. And I have the impression that “a low-resolution thumbnail” is saved after browsing the first time a directory, to allow a better off line experience.