What type of phone do you have? That makes a difference.
My opinion (as I’ve been running all 3 for over 5 years) is that Amazon Alexa is better at receiving and completing commands, Google Home is better for answering questions and with people in the home who aren’t as tech savvy, and Siri is better for an overall smarthome IF your devices are compatible.
If you had no issues with Google Home and you’re using less than 5 smart home devices I’d say just pick up another mini.
Not at all. I’ve got over 140.
The issue is more what you want them to do and how to want to interface with them.