VLAN tagging and Google Wifi

I recently got Google Wifi and had it all set up on my network just fine, connecting through a D-Link Router on Voyager fibre. I asked Voyager to disable VLAN tagging so that Google Wifi could connect directly to the ONT.

That's all done and it works perfectly fine.

My question is: What's the risk/benefit to having VLAN tagging enabled or disabled. Couldn't find much online about this.