Create multiple new labs

The best way is to use the BulkOperations scripts. Here is a link to the examples https://github.com/Azure/azure-devtestlab/tree/master/samples/ClassroomLabs/Modules/Library/BulkOperations/Examples this will let you create lab accounts, labs, etc from a csv file. As for the VM sizes it looks like you want either a Medium (nested virtualization) or Large (nested virtualization) . Here is a chart of the friendly names vs the api size. https://github.com/Azure/azure-devtestlab/tree/master/samples/ClassroomLabs/Modules/Library/BulkOperations#virtual-machine-sizes

Hope that helps,
Roger