You’re welcome Rudi!
That should work.
Ah I see.
To be sure you can ask the community how much MB’ certain apps use @ their Homey.
But as you can see, many apps stay below 10MB’s.
Athom states in general an app uses around 15MB’s.
Some apps tend to grow and grow, for these you can easily restart them automatically via a flow, at a convenient time (which is not always while you try to sleep 
)
You can use zones for that. Or timers. Some aqara and tuya sensors “pause” for one minute after a motion detection.
To view what your flows are or aren’t doing, I add a Papertrails log card to every THEN and, if used, THEN ELSE action.
This can be done in one go luckily (in Dutch).
(There’s sadly no user viewable Homey log. Only Athom can view it when you send a “diagnostic report” at their request).
Also the phone app device timeline shows what / who switched a device, which I already mentioned.
Looks promising:
You could consider to connect your domotica Wifi to the guest network, or a dedicated vlan. If ‘they’ might want to check for interesting stuff on your network, it’s at least a lot more difficult 
If it has a 3 position switch, there are solutions available using a 2-gang or 3-gang relais.
