Hello @RNA and welcome to Microsoft Q&A.
There is no "Microsoft policy imposed limitation" on your throughput that I know of. No data cap like in a mobile phone plan. That said, there are other limitations which happen.
You can run into hardware or software limitations. The Integration Runtime lets you specify the compute power made available for Data Flows, and I have seen people sometimes push too much and make it choke. The Copy Activity lets you specify the number of Data Integration Units (DIU) (compute power used for transfer), and this mostly affects amount of parallelism.
More often limits are hit on either the source or sink ability to accept connections.
There are limits on number of concurrently running pipelines, concurrent external activities, and concurrent DIU. See azure-subscription-service-limits
Correction: There is a maximum number of DIU in a single copy activity, and given that DIU affect the amount you can do in parallel, this is an indirect limit on simultaneous data.
Data Integration Units per copy activity run 256