The problem was that my MainWindow (the container of the PlotView) has a LayoutTransform:

Me.Scrll.LayoutTransform = New ScaleTransform(ScaleX, ScaleY)

So, I put to the PlotView:

Plot.LayoutTransform = New ScaleTransform(1 / ScaleX, 1 / ScaleY)

And with that the plots are not deformed in both monitors.