I agree about separating the services. In the past I had problems upgrading owncloud/nextcloud with too many plugins. It was difficult to keep all data between the versions.
Now I’m using Baikal for calendar/contacts, Silverbullet for notes and Linkding for bookmarks.
Currently I use these services by VPN only, so file sharing isn’t really useful. I could reach all my files there by SMB and I don’t dare to provide my services openly. For that alone Nextcloud was great, but I don’t trust my setup enough to share it with the world again.

Please checkout Silverbullet.md.
Native markdown support, folder structure, customizable by css and some script language.

Big butt plug, eh?