How to leverage a desktop iMacPro with a Macbook Pro?
I would use NoMachine for macOS for this.  

Basically, install NoMachine on both computers, and setup the MacBook Pro as a NoMachine server (and note the IP address).  Connect to it from the iMac, and you'll be able to quickly switch control between the two computers with a keystroke and mouse-click.  You can control the MacBook Pro almost as though you sitting at the console: either in full screen or a separate window.  NoMachine is very configurable: it forwards audio, connects to local devices, etc.