I will answer your questions one by one as below:
Question 1). Can I host 2 concurrent MS Teams meetings running on separate machines at the same time?
Yes, you can. I have verified this in my lab. The two meetings works well.
Question 2). Is there a limit on the number of concurrent meetings that I can host?
Do you mean in the same machine or different machine?
If you mean in the same machine with same client, the limit number is 4. When the number reaching up to the limit, it will show the following warning message:
If you mean in different machines, I tested in two web clients and five desktop clients and they can start Teams meetings well. Then, I have an assumption: user can start Teams meetings on 5 PCs or Macs, 5 tablets, and 5 phones at the same time. The total number is 15. The is because with Microsoft 365, user can install and sign in to Office on 5 PCs or Macs, 5 tablets, and 5 phones. The following is the evidence in official document.
If the response is helpful, please click "Accept Answer" and upvote it.
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.