I'm not sure if you have seen Wolfgang's Channel on youtube, he has cool contents on building NAS but one of the videos was interesting and came handy on building SOHO NAS (at least for me). There is a German forum that the whole community is working and keeping tabs on their NAS consumption and keep posting their findings in an Excel sheet which shows the builds that are under 30W. Big shoutout to each and everyone of them if they ever see this comment. It's candyland there, you can even find builds that idle at 6 to 7w !!!
Here is that video, around 2:28 if u want to save time but i would suggest watching the whole video even though it's long
Here is the thread,
and here is the sheet