If you want to use the software on a third computer, you will need to sign out from one of the two currently activated devices. Adobe provides a mechanism to log out remotely if needed.

If you have installed Adobe apps on an external hard drive, you can move that hard drive between computers. As long as you are logged into your Adobe account on the new computer, you should be able to run the applications from the external drive

You cannot run applications simultaneously on more than one device with the same license. Therefore, if you're using Photoshop on one Mac, you cannot use Illustrator on another Mac at the same time with the same account

While you can install and move Adobe apps via an external hard drive across multiple Macs, you must adhere to the activation limits and usage policies set by Adobe.

I hope that it would be helpful to you.