Use the attached sample project.

Sceen 1 (Screen with program shortcuts) on the right in the gif: this screen has display scale 125%

Screen 2 (Screen with the Form) on the left in the gif: this screen has display scale 100%

When all three toolwindows are placed in the forms, there is no issue. The Dropdown list of ToolWindow1 (floating, dockable..) when opened is placed correctly.

If I moved the ToolWindow3 from Screen2 to Screen1 and make it the most recent active window (by clicking on it), I go back to the Screen2 and open the dropdown list of Toolwindow1, this list's position is now wrong and the text size bigger. This is because it takes the display scale (125%) of  the screen where the most recent active toolwindow (ToolWindow3 ) is.

If I popup the ToolWindow2, place it in Screen2 (the same screen with ToolWindow1), make ToolWindow2 the most recent active window, and open the dropdown list of Toolwindow1, this list's position is now correct and the text size normal. This is because it takes the display scale (100%)  of  the screen where the most recent active toolwindow (ToolWindow2 ) is.

Workaround: add app.manifest file and declare the application as DPI aware: