If you start on a free plan but then ultimately switch to another provider do you have any idea of how hard it would be to export and import all your tasks, files, etc?
Application data depends on the app. For example, Notes [0] save your notes as Markdown files so you can move them (along with your files) wherever you want. However, News [1] don't and don't have export/import features at the moment either [2].
Nextcloud as a file storage solution and a non-collaborative office suite is great, but I cannot recommend its apps the same way. They are very convenient to install, but the quality varies a lot in my opinion so evaluate before you adopt.
[0] https://apps.nextcloud.com/apps/notes
[1] https://apps.nextcloud.com/apps/news
[2] https://github.com/nextcloud/news/issues/2503#issuecomment-2...