Here is a readable list of PLATFORM_IDs
https://github.com/spark/firmware/blob/develop/platform/shared/inc/platforms.h
And you’r right 10 is Electron which is currently the only one that features that sleep mode.
As it turns out you got similar advice about sleep modes of @BDub here as in your other thread 
How to get Electron to publish value if value has change by more than X, and then enter deep sleep?