Hey ggoble,

It's my understanding that you want to have resource groups with your systems that are directly dependent on each other. So you have it right when you say the WebApp and DB should be in the same resource group. This probably explains the benefits better, https://docs.microsoft.com/en-us/azure/azure-resource-manager/resource-group-overview, but one of the benefits we've taken advantage of is the fact that you can completely clean up an application by simply deleting the resource group.

That said, you can group your resources however it makes the most sense for you.

I hope that helps,
Steve