WPF vs WinForms

https://www.infragistics.com/community/blogs/b/devtoolsguy/posts/windows-presentation-foundation-vs-winforms

Reference a .NET Core Library in WinForms Application

https://www.hanselman.com/blog/HowToReferenceANETCoreLibraryInWinFormsOrNETStandardExplained.aspx

Try to use the DotCoolControls

https://github.com/jontiefer/DotCoolControls

Open Source WinForms

http://nugetmusthaves.com/Tag/WinForms

OpenWinForms

http://www.openwinforms.com/

OpenWinForms is a open source website for windows forms and controls. Here you can find windows controls and libraries for free. This is a non-commercial open source web site. This site mainly focuses on Microsoft technologies e.g. Microsoft .net, VB.net, C#.net etc. You may use these for any commercial or non-commercial purpose for free, however you cannot sell them directly or by modifying.