Immich has image and facial recognition by default and a very neat Android app. Also it’s running in my home server, which has more power if Immich needs it. In that case I’d say software should serve one purpose and serve that good. Immich is just for picture management and does that very good. Nextcloud is a cloud and the Photos app is just a small extra that can’t compete with a full-fledged software. Nextcloud runs fine on my Raspberry Pi 4, but it’s only used by me and three friends. It’s mainly limited by your network speed and disk speed I’d say. And I’m using an external hard drive without issues.