As for Nextcloud vs a restic server, Nextcloud is heavier, but I do benefit from it's extra features (like Calendar and Contact management) as well as use a couple of apps (Memories for photos is quite nice). Plus it's much more family friendly, which was a core requirement for my setup
As you said, everybody will have their own approach. For me, setting up a dedicated firewall to protect the soft underbelly of my less tech savvy family computers was the primary motivation for starting a home lab. I could not imagine a network architecture without it.
Why did you go with Nextcloud instead of using something more barebones, for example a restic server?