I knew there had to be an option to keep from having to specifically activate what project runs when debugging in a solution, and there is...
Right Click on the solution and open Properties.
There you should see an option to run the selected project versus the default 'Single Startup project' that gets updated each time we select and set a specific project as the startup project.
Change that option (radio button) to 'Current selection' and whatever project is selected in the Solution Explorer at the time of running debug (or release) should run.