eljudio42 wrote:
I'm assuming each device would be able to detect its own partition correct?
Not necessarily. If the partition is readable on both the Mac and the iPad, both partitions would be available to both devices. I don't believe you can "lock" a certain partition to a certain kind of device. You could simply name each partition to something that would be recognizable to you such as "Mac" and "iPad" if you wanted to keep each partition dedicated to each device.
You can run apps from external drives on MacOS but the drive needs to be formatted as APFS. Google is helpful for the details.
The iPad requires that the app be installed on the device's internal storage so you can not run apps for the iPad from an external drive.
You can access files stored on either partition from either device using Finder on the Mac or the "Files" app on the iPad.