Hello David9
Welcome to Microsoft Q&A Platform, thanks for posting your query here.
Based on your requirements, I would recommend using a Standard_D series virtual machine in Azure. These should be sufficient to run 20 strategies in MultiCharts, TradeStation, and Interactive Brokers.
https://learn.microsoft.com/en-us/azure/virtual-machines/dv3-dsv3-series
Additionally, you may want to consider using Azure Premium SSD storage for better performance. You can also use Azure Managed Disks for simplified disk management.
It's important to note that the optimal VM plan may vary depending on the specific requirements of your trading strategies and the workload of your live trading account. I would recommend testing your workload on different VM sizes to determine the best fit for your needs.
I hope this helps!