C# Static Class vs. Static Var (BestPractice) : I have a WinForms App with a few Vars [Panel MainPanel; Int PanelWidth;] which I will use in different functions in multiple Classes. 

[I read in some Forums to avoid making Static Classes, not sure exactly why and I wonder if this pertains to Static Vars too.]

Is it best practice to just declare these Vars as Static Vars in Form1

('public partial class Form1' is the default opening Class for all WinForms Apps)

Or is it better practice to make another (non-static) Class 
-for example: 

    public class VarClass
and declare the Vars there as:

    public Static Panel MainPanel;
    public Static int PanelWidth;
Or 3rd option to make a Static Class
 -for example:

    public static class StaticVarClass
and declare Vars there (also with 'public static' keyword)

    public Static Panel MainPanel;
    public Static int PanelWidth;
    
What is the best practice for performance and/or what are pro's & con's of each?