Hello Naveen!
I converted the Lionel tank cars with sound to two rail myself. They retain sound. I can't trigger some of the Legacy effects as I don't have their controller. I like that they add another dimension to the train. The grandkids even noticed when I add them on.
Every engine in the video is MTH. I converted the 2 Ac6000s pwd and dummy awhile ago (3 yrs?) and the CR SD80MAC is my newest diesel conversion. I did not finish the Mac, as even the coupler box surround is not even painted! I did not extend the handrails either. I'm happy to get the engine I'm after sometimes, even if it's not perfect. The older MTH diesels have to have the pilots mounted to the metal frame. The newer ones have mounts on the shells to accept the pilots. Making a simple shim works, I like to cast the whole pilot when I can to get the steps correctly spaced.
Swapping the wheels out, and removing the three rail couplers is a snap. You can't mount KDs until the pilots have been fabricated or re-mounted.