You are already comfortable with testing in your hand, so the best test is to add just enough power to make it hover in your hand. It should feel like it is very stable and will just lift out of your hand.
If it feels like it is trying to twist out of your hand, then you have come stabilization reversal. It is critical that you find and fix this.
The order of the motors on the Vehicle page must be followed exactly and the ESC signal wires must be plugged in in the correct order and the CC3D must be mounted with arrows pointing forward and ESC connections on top side right side.
We are hearing reports that there may be some new CC3D that need different mounting though.
To check stabilization direction, look at "Flight Data" page. Top left window pane shows view from inside the model. No need to run motors, just check that it is level when model is level, that you see more brown dirt when you tip it nose down, and that the roll looks backwards, room tilts left when model tilts rightward. You can also check that yaw/rudder rotation is in the correct direction on this display.