I use a lot of the apps. Most of them are “just good enough” to keep from installing alternate, standalone versions. However, having them all integrated into NC is a big plus over maintaining separate applications.
Calendar app and sync it with my phone with DavX5
Tasks -> DavX5 -> OpenTasks on my phone
Deck, which is a Kanban/Trello type of task management.
SnappyMail app to access my email
The Nextcloud app on my phone handles automatically uploading my photos and videos.
The Riotchat app keeps me connected on Matrix
Passman to manage my passwords (also has a dedicated Android app)
Music player to play my media (works great as a Chrome app)
Cookbook app for my recipes (it is also good at scraping/importing from recipe sites if you paste the URL in)