I used Nextcloud for both files and my PortableApps for years but it always had a hard time managing all those tens of thousands of small files. Lots of sync overhead. So I found Seafile and couldn’t be happier. I don’t just have my PortableApps in there now, I sync my Windows Documents, Pictures, Videos and Downloads folders. Seafile is very good at tracking partial changes in files so it doesn’t always need to sync an entire file when just part of it changed.

Also: It’s just a file sync service without any auxiliary features.