I seems to often work to 15cm, it has a claimed accuracy of 90%.

Could be interested.

Yes 3D drawings are X, Y, Z to give a plan in 3D. Its not normally as simple as changing Z to 0, but there is formula that will do the translation, what is your need?

Yes see https://developer.apple.com/forums/thread/708591

The apple RoomPlan can not be extended but you can add your own library and make it operate alongside RoomPlan, I am currently adding Yolo3 objects to the recognition process, to create an extended recognition, including boxes.

The XYZ model that is created by Roomplan is perfect for CAD. We have found the accuracy to be within 3% (apple quote 10%) Yes items are tagged