I am new using Unity and build a UI for Android. It looks ok but i need to switch platform to create a PC version. When I change the platform and build the project, the size and position of the controls change and the new position and size looks very bad.
I guess you are using a Canvas for your UI, in this case you can go to the Canvas component and choose UI Scale Mode > "Scale with screen size". If you dont choose this option, the UI elements inside your canvas will look bigger or smaller depending on the screen resolution.