The camera in Take Photo widget should be turned off until it is needed

The camera should be turned off until it is needed. Also how do you choose which camera in used. My tablet used the facing lens, despite the camera using the away facing lens when it is opened separately

You can add conditions to hide the widget unless its needed depending on your scenario. Please refer to the guide below for more information on conditional logic:

Smart-Forms-Using-Conditional-Logic

As for your other question, I'm not sure I understand it correctly, we have recently added a fix that should let you choose the front or rear facing camera when you open the widget. So it should be possible to choose the camera now.