LightningPay package contains all Lightning cliens (LND, LNDHub, LNBits...).
It's the ideal starting point for .NET client application (console, wpf, mobile) that not use Dependency Injection or if you want to instantiate the client yourself.
Use directly LightningPay.DependencyInjection for all your app projects that use Dependency Injection (Web API, Web App, Worker Service...)
LightningPay.Abstractions is for your all library (non app projects) to avoid to add strong reference to the lightning clients.
You can built also your extension methods to the ILightningClient interface to extend your lightning client.