I’ve been running a btrfs storage array with data on raid5 and metadata I believe raid1 for the last 5 or so years and have yet to have a problem because of it. I did unfortunately learn not to fully trust the windows btrfs driver but was fortunately able to restore from backups and redownloading.
I wouldn’t hesitate to set it up again for myself or anybody else, and adding a UPS would be icing on the cake. (I added UPS to my setup this last summer)
Hard drives, especially spinning discs, and RAM are probably the biggest factor at idle. I dropped my servers’ idle draw from 220w to 180w by dropping it’s RAM and replacing some older drives.