If your camera is a “Perspective” camera….you can have the menu lock to the cameras view using the function of “Fit to Camera Edge”. You take your menu item and parent it to the camera. You will then need to Clear Parent Inverse for that object and then you will see that the object regardless of where you move the camera stays in the correct position based on the camera…not the background. The menu will scale based on the screensize but you may need different layouts and porportions.
To proportionally scale the menu system based on differet aspect ratios and screen size…. you can create cloned versions of the menu system and use Visibility Break points to display them based on the resolutions you want. This will allow you to create scale and reposition the menu items where you want for each break point you create.
Alternatively…you could just do your entire menu system in HTML as an overlay to the V3D container and use standard HTML/CSS to control the menu size.