Be aware, that getStateInformation are used by the host to read the plugins state when saving the project and setStateInformation when opening a project/session. Then the state is in your AudioProcessor (aka PluginProcessor). But it is your responsibility, when the editor is opened to transfer the actual values from the processor into the editor’s widgets.
Especially the methods you use getNumParameters etc. are or will become soon deprecated. If you are starting you should definitely use either subclasses of AudioProcessorParameter and create them with AudioProcessor::addParameter() or even better an AudioValueTreeState, see e.g. thread: How to use AudioProcessorValueTreeState's SliderAttachment? - #5 by mashu
You can either call setValue for each widget in the editor’s constructor, or you create an e.g. SliderAttachment, which will keep your slider in sync with a processor parameter. To use this use the AudioProcessorValueTreeState.
HTH