For Parallel Test Execution I need "NUnit" but I also like reports from SpecRun. Can anyone please help me to guide How to mention two UnitTestProviders in App.config.?
No, it is not possible to have both unit test providers.
For running the Scenarios in parallel, you can also use SpecRun (SpecFlow+Runner). It has much more features than NUnit to execute in parallel.
Here are a sample for the different test thread isolation modes: https://github.com/techtalk/SpecFlow.Plus.Examples/tree/master/TestThreadIsolation
Full disclosure: I am one of the developers of SpecFlow and SpecFlow+.