I have been using an old PC as NAS and running docker containers (Immich, Nextcloud, paperless-ngx etc.). I got 5 3.5" HDD disks and a Nvme. Even on idle, I am consuming 50-60w. A friend of mine is selling a Qnap NAS which is a dedicated machine and probably consumes less power, although I don’t know if it’s worth it.
You can only spin drives down if they’re idle. If you have a service that touches it - say, homeassistant logging data, tvheadend updating EPG - then they’re going to keep spinning.