So, we have the application and we want to do load test. Before we do a load test, this is five things that you need to need to consider before you want to do load test.
#1 Load testing doesn't support UI Code testing (for Now)
If you want to do load test with specific activity such as buying or shipping. You can record to the UI Coded testing but you can't do that on a load test.
#2 You can't differentiate between real user and load test
If you are on the same region with Azure DC you can't differentiate the IP address of load testing and IP address of real user. Therefore, it is recommended to use the load test before the system released.
#3 load test is a good way to DDOS your system
Yes, this load test can be also to do initial penetration test. Just do with 1 K users with different configuration
#4 Load test won't hurt your Azure cost
Load test is cheaper than VM. Please see the price
#5 Load test is better developed on Visual Studio Enterprise 2017 rather than Visualstudio.com
If you want more features and more testing model you can use VS rather than the online version of visual studio. But if you want simple configuration go on visualstudio.com you will get what you want