I intend to use 3S to backup my website in addition to local backups, but not for uploads as I don’t think it would be really useful, but I need to think about that more and search for more information.
Hetzner servers are scalables and I can upscale/downscale in seconds (can’t decrease disk size though), but I prefer to start on right specs estimation than doing things 100% empirically. 
Also my uploads take 7 GB of disk size.
Thank you very much for this quick explanation. My community is international, so it will probably help.