Welcome to the community and thanks for contacting us with your question. I'll be happy to answer that for you.
So the good news is that the Google and Nest WiFi networks run both 2.4GHz and 5GHz bands simultaneously and you actually don't need to choose between them. The mesh network creates a hybrid network that will run both bands across the entire network and your devices will automatically connect to the best network for their performance.
If you have any other questions, please let me know. Thanks.