It depends how you look at things. Having a device such as a NAS and expect it to hibernate is something that was always puzzling to me why people are bothered with that. Then again I get it, but do keep in mind that there is a lot of services and packages that will wake up your nas.
I also have a couple of RPi's as well and it works perfectly, don't get me wrong, but I always find backing them up difficult compared to Docker. With Docker you have an image and volumes and that's it. You can move these relatively easily from system to system.
How can you easily backup the RPi? With dd or something like that?
Yes, i have seen those but in my experience it is a hassle. Incomplete backups, interruption of service. That is why I prefer Docker deployment nowadays. I have some dedicated RPi's in the house for home automation, media play but in case of a backup/restore there is always trouble. In my experience.
The strategies to backup the Pi have been lacking. I use containers on both the Synolgoy and Pi's to run apps since I can easily backup containers vs. the Pi and native installed apps. I rarely now install anyting in the base OS outside of network commands and editing tools.