You will burn more calories at higher intensity. There are studies that show that interval training (max/sub-max intesity @ 1:1 ratios) do more for overall fitness (and burn more calories) than exercising at the fat burning and higher aerobic ranges.

They have said that 20 minutes of exercise is the baseline for fat burning – this is a bit of a misnomer. You burn calories/not fat. Though, you can manipulate “fat burning” by diet and working out at specific times, it is recomended that you research a little bit on your own.

The “fat burning” range was adopted for lazy people as a guidline for recomended minimal intensity.

probably yes.