Nextcloud itself is free and the difference is just in terms of support. There is the notification function for the mobile apps, that pass through a Nextcloud company server that are limited for personal users (free use policy up to 500 users):
(if you don’t have to use this feature).
For the office solutions, the default (pre-build) images had some limits as well, usually a number of parallel users (10 or 20). You can build your own images without these limits):
If you want customized desktop/mobile clients, with subscription they can help you. Not sure if you could do all by yourself, the code is open source, so it might just be a bit more painful.