Guest access (Controls)
I think I understood that guest access could be controlled. I'm a month onto eero (loving it) and last night enabled Guest Access & put a retired android phone online. I thought I understood that eero has controls (say for a renter) to setup a time window (say Saturday noon to following Saturday noon) to be online as a guest.
Secondly... pretty sure Guest gets internet only and cannot run Roku, AppleTV, Sonos, or printer on the main network
You have to create a Family Profile for the devices you want to control. You can schedule “pauses”. The problem with how profiles work (and this currently my real only, but big, frustration with eero) is that you have to manually add the device to the family profile. You can’t create a family profile and set it to automatically apply to all unknown/new devices. So for your renters situation, you would have to know what each of their devices are. And if they bring a new device onto your network, you’d have to manually add that to the specific profile for it be controlled.
To answer your 2nd question, yes, the guest network devices are isolated and can only access the internet. Nothing else.