Its a good idea as standard ip cameras have way more features so you don’t have to make compromises. Instead of using a shelly, I would recommend you choose a camera that supports ALARM IN and OUT terminals via an API and also smart line crossing alarms. You can use the alarm in terminals to notify openHAB when the doorbell button is pushed and also to trigger recordings in a stand alone mode without needing openhab to use rules. Standard cameras also have PRIVACY block out areas so you can black out areas so they can not record parts of the street or the neighbors windows for example.
When choosing a camera and the location, you have to consider what happens if someone walks to your door wearing a hat. Keeping the camera down low allows you to see the face of someone that has a hat on, and makes cleaning spider webs off the lens easier.
To learn what features from different brands are implemented, see this post:
IpCamera: New IP Camera Binding - Add-ons / Bindings - openHAB Community
Check out the two programs for a tablet:
fullykioskbrowser
And habpanel viewer
HABPanelViewer 0.9.27 - Apps & Services / HABPanel - openHAB Community
Streaming camera to google home devices can be done, but you will be far better off in the long run setting up your own solution using the above. More local, private and flexible whilst staying around the same cost. The above apps can put the screen in sleep mode until it detects a person in the camera on the tablet and it will then wake up the screen, lots can be done I just don’t have experience with them as I use the Google solution for now as we got one of them for free on a deal.