This is fine (there is actually no limit on resources per resource group) but might not be the optimal approach. In general, you'd structure your resource groups to reflect your delegation model and resource lifecycle. In other words, if you want to delegate permissions to some of the resources (not all of them) to someone else, then it might make sense to create a resource group for it. Similarly, if some of the resources will be deleted earlier than others, you might want to create a resource group for them as well. Another potential reason is to organize resources in the manner that reflects their intended use. However, there are no hard rules regarding this - so ultimately it's your decision.
More at https://learn.microsoft.com/en-us/azure/azure-resource-manager/management/overview#resource-groups
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hth
Marcin