Something to note: because they are “online”, smartplugs will always be a vampire load of sorts themselves.
Wemo/HS110 seems to clock around 1.5w and the HS300 I assume is probably north of that (especially with all LEDs on) but I haven’t measured it. To nix that load you would need to unplug the smartplug/strip altogether.
The relays in the switches are relays so they do cut the power load (to 0w) … whether you manually or remotely switch the switch on the outlet. Let’s hope!
The HS300 has per-plug device monitoring through Sense … i.e. you’ll have 6 independently switchable/monitorable devices. One caveat is that if you get enthusiastic about adding lots of HS300s you might hit the Sense processing limit. @kevin1 brings that up here