I guess that depends on your preferred way of working.
If using Overbridge, your Motu is not relevant apart from as an output. Or am I missing something here?
If you are mostly using USB/Overbridge and your DAW, then I’d settle for that. Doing all the routings within Live. That’s a flexible way to handle things.
But if you wanna use the A4 and Heat without firing up your DAW, then an audio (line cables) connection is smarter. And you could use your Motu (well, depending on model) as a digital mixer without the DAW.
In my setup, the Heat is one tool that does not have a permanent connection. I make case by case decisions. Right now it’s on the output of my modular and fed into my Motu where I feed it to its own channel, but also to the inputs of my Octatrack. But no DAW or Overbridge. In this setup.
Both your scenarios are valid and doable. But what are your needs and preferences?