We currently have an Echo and 4 Echo Dot's
We have two Adult Amazon accounts in an 'Amazon Household' (the maximum I understand possible with Amazon, query raised with them by the way).
We give commands to any Echo device from any room against any Zone / Room, at any time by anyone.
I added the Honeywell Skill to both accounts in the Amazon Household with the same Room / Zone names. As otherwise it would be inconsistent and probably very confusing.
The two Amazon accounts in the Amazon Household are using 1 Honeywell account.
We have 1 Honeywell Evohome Connected Thermostat Pack ATP921R3100 and 10 valves (HR80's) with some Honeywell Homecomfort timer valves on additional radiators in bathrooms. Some Zones use multiple valves. No it's not a mansion (maybe an Englishman's castle), it's just well insulated rooms in a modern house, in a cold wet part of England.
The two Amazon Household accounts are used as ordering, play lists, favourites and music are seen by Amazon as for individuals. My wife 'pays' for Amazon Prime, so to access Amazon music I have to 'Switch to her account' or pay multiple times. Whilst I buy things like Echo's and Dot's, run the heating system accounts and other similar stuff I am interested in.
You can perhaps see the number of possible combinations of options is significant.
An alternate to the above scenario, the use of one account or very separate accounts against each Echo device would of course work nicely. I guess it depends if it really is a Household or not. So I could have had all devices on separate every things and thus isolated operation. Then we could not share the Amazon music with the children (they are over 16 now)... And my nice Alexa help page on our Intranet would get very complicated....And it would be a pain to administer, as no one else would do it and we would loose the flexibility of how we are using the house as the children make forays into the wild (well University at least). The kids could still run into another room and tell Alexa to turn off the heating! Thus probably immediately defeating the object of trying to run things independently! (If they can remember the 4 digit purchase pass code, they can order anything they want while they are at it. As both have IQ's well over 150, they probably already know it and I have forgotten).
I think my main observation is that Amazon don't really cope well with my concept of a 'Household', I tend to think their interpretation more as 'An association by two individuals'.