Heat transfer between two bodies
 

I have two blocks separated by a small distance. I initialize the bodies with 30 degrees and patched one body at 500 degrees. I am trying two methods to solve this.

I create the two bodies and fluid domain, then create interfaces where required.
Another is selecting all bodies on Design modeler and making them as a single part. This creates them as walls with coupled condition for thermal.

Are these methods correct and same?