Hi!
That's not possible. Adapt your settings for camera and resolution, or better use Batch Render or Render Sequence.
The main purpose for playblast is creating a realtime preview of your scene / Viewport.
Turn off every gates ( resolution gate and film gate ) and on play-blast settings choose " display size " to " from render settings".
Don't forget to choose your desire resolution in the render settings and hit play-blast.
all thread I know, but there is no use rendersettings res for when you export shots within the camera sequencer, it is really annoying.