Please, find attached a small example. The speed would not depend on the presence of additional Y axes. I must note, that speed is influenced by the series definition settings. When showing line series with lots of items the visual tree becomes loaded with elements and that might lead to a certain delay. RadChart features an "optimized" mode for rendering Line/Spline/Area and "alike" series, which is automatically turned on when no labels, pointmarks and tooltips are shown.
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