Ive run Nextcloud on a Pi4B with 4GB ram & external HDD with just one user. I also sync Joplin notes, which use constantly. I also used Collabora Office on the phone for syncing office docs. No real issues, synced between a couple of desktops & a phone.

Eventually treated myself to a Pi5 8GB ram with NVMe & an Argon fanless case. Main reason for upgrade was an additional Nextcloud need - to share holiday/trip/event photos with multiple non tech savvy older family members via the Memories plug in. This set up has been absolutely rock solid, absolutely no issues & for my needs has been blazing fast. Memories is great too for quick & easy sharing whilst away. The family members love it (Nextcloud is exposed behind Nginx Proxy Manager, I send them a read only public link)

As they are quite intensive I recently migrated Immich & Paperless from Pi4B 4GB to a Beelink EQ14 but I see no reason at all to migrate Nextcloud from the Pi5.