Which camera angle for Mira 7?

Try this:

Open the lid of the laser
Locate on the open lid a location that could look down close to the center of the bed. Normally this would be near the folded edge of the clear acrylic.
Measure the height from that spot to focused bed
Input your bed size into the Help->Camera Selection Help tool and then use the measured height to determine applicable cameras for your situation. If multiple cameras meet the criteria then higher resolution is preferable. Camera aspect ratio closer to your bed size are preferable. And lower FOV angle is preferable to wider angle all other things equal.