Any performance concerns with running Jamf Protect and Microsoft ATP concurrently?

I guess it depends on how you have both configured. Here is what Microsoft has to say about other products running alongside Defender:

Running other third-party endpoint protection products alongside Microsoft Defender for Endpoint on Mac is likely to lead to performance problems and unpredictable side effects. If non-Microsoft endpoint protection is an absolute requirement in your environment, you can still safely take advantage of Defender for Endpoint on Mac EDR functionality after configuring the antivirus functionality to run in Passive Mode

This one is really down to what you tell the applications to do, and how you configure things. JAMF Protect can grind the system to a halt by itself depending on what you have it do. Poor scripting for your analytics can also cause undesired performance impacts. We had to exclude JAMF Protect from our other security clients, as they would get into the middle of everything JAMF Protect does and cause CPU usage to spin out of control. 

My suggestion is to toss both the clients on a test device, configure them and let them go to town and see what happens.

I am wondering if someone could answer the following question:Currently, we have a Microsoft (MS) Managed Service Provider (MSP) and Managed Detection and Response/Security Operations Center (MDR/SOC) team running Defender on our Apple fleet. I would like to know to what extent Defender is still necessary when running in parallel with Protect, since you can send the data from Protect to Sentinels.What is the purpose of Defender in this setup? And if we continue with both agents on endpoints, what are your experiences or any advice you may have?Thank you for any insights!