Which WiFi mode is best for 2.4 GHz?

Use Windows to channel-surf and find the best signal to use
For the 2.4GHz network, choose channels 1, 6 or 11.
For the 5GHz network, choose channels 40, 80 or 160.
You can also leave it set to automatic or default settings if it seems to be working fine.
If you have questions or need any assistance troubleshooting, just visit: Router Help | Google Mesh Setup