What's the difference between "napping" and sleeping? Once you truly power down all the I/O they should perform about the same. A tablet with all the radios powered down (via airplane mode if necessary) can "nap" for a long time, rivaling any laptop with its proper "sleep".
https://en.ittrip.xyz/windows/modern-standby-vs-s3
There’s a Linux command for listing supported sleep states, but I don’t have it handy.
cat /sys/power/mem_sleep