Flutter: How to have two variable sized containers overlap without using specific positioning on screen?

Okay, so this is a bit of a difficult one to explain.

I would like two TextFields right above/below each other. The problem comes when you type in to one of the TextFields and the result should be shown in a variable-sized container above other content WITHOUT pushing other content down.

I could just use a Stack with Positioned, BUT then I get problems with exact positioning because of different screen-sizes, fonts and text-sizes on devices. If I use a Column, the content gets pushed down.

See the screenshots to help understand my problem (code further below)

This is what it should look like for all screens / sizes / fonts / etc.
I can get this result with Stack+Positioned, but I get the problem illustrated further down. (the red box is the variable sized result container).

This is what happens when I use Stack+Positioned and the text-size is increased on the phone (or font is different, or something else like that).

This is what happens when I put the TextFields in a columnn.

Code

This is obviously just example code. In the real app, we have two address searches that calls an API to the the result list.

class StackProblemExample extends StatelessWidget {    

  @override
  Widget build(BuildContext context) {
    return Stack(
      children: [
        Positioned(
          top: 82,
          left: 0,
          right: 0,
          child: TextFieldAndResultList(
            hint: 'To',
            isTop: false,
          ),
        ),
        Positioned(
          top: 20,
          left: 0,
          right: 0,
          child: TextFieldAndResultList(
            hint: 'From',
            isTop: true,
          ),
        ),
      ],
    );
  }
}

class TextFieldAndResultList extends StatefulWidget {
  final String hint;
  final bool isTop;

  const TextFieldAndResultList({
    super.key,
    required this.hint,
    required this.isTop,
  });

  @override
  State<TextFieldAndResultList> createState() => _TextFieldAndResultListState();
}

class _TextFieldAndResultListState extends State<TextFieldAndResultList> {
  var controller = TextEditingController();
  var containerHeight = 0;

  @override
  Widget build(BuildContext context) {
    return Column(
      children: [
        TextField(
          decoration: InputDecoration(
            hintText: widget.hint,
            border: OutlineInputBorder(
              borderRadius: widget.isTop
                  ? BorderRadius.only(
                      topLeft: Radius.circular(10),
                      topRight: Radius.circular(10),
                    )
                  : BorderRadius.only(
                      bottomLeft: Radius.circular(10),
                      bottomRight: Radius.circular(10),
                    ),
            ),
          ),
          controller: controller,
          onChanged: (value) {
            setState(() {
              containerHeight = controller.text.length * 10;
            });
          },
        ),
        if (containerHeight > 0)
          Container(
            height: containerHeight.toDouble(),
            color: Colors.red,
          ),
      ],
    );
  }
}

How in the world could I achieve that the tow TextFields (with each their own result container) can be stacked after each other without concrete positions AND not push each other down?