What is the difference between Jamf now and Jamf pro?

Jamf Pro is a more powerful tool to manage iOS & MacOS. Jamf now if very limited for regular users use.

Jamf Now is specifically for manage Apple mobile devices in a small to medium environment and Jamf Pro integrates MDM for Mobile Devices and Apple Laptops for large enterprises.

Jamf Now is less expensive, but also much less powerful - think of it as "Jamf Pro Lite." It is designed to be a management framework for non-IT to quickly deploy, upgrade, and redeploy Macs as well as mobile devices. Now doesn't allow running scripts on enrolled Macs, and doesn't have anything comparable to Pro's "Smart Groups" (device membership is based on device conditions, such as free disk space or currently installed version).

Jamf Now is a very basic MDM for a small fleet that just needs to manage a few devices. Jamf Pro has a binary that runs on each endpoint allowing you to completely control macOS devices remotely. Jamf Pro also integrates with the other products from Jamf. Jamf Now does not.