Honestly it's probably both. Each breath will contain some amount of virus baring particles at a relatively low velocity. Each cough and sneeze will release more virus baring particles with a greater distribution of sizes and velocity.

It's key to remember that the 1.5m (or whatever rule) isn't about making you 100% safe, it's about sufficiently reducing risk. For example, if standing at normal (2-3 feet) distance has a 1% chance getting you infected, and at 5-6 feet it has a 0.1% chance of getting you infected, that's a huge win.