What is the recommended FPS for an NTSC Laserdisc? Does it matter? Set it 60fps, 30fps, 29.9fps, or another fps?

The "hardware" frame rate of USA NTSC video (from a USA laser disc player) is 59.94 fields or 29.97 frames per second. I do not know if Virtualdub does any of its own processing of captured video, though. If it does things such as deinterlacing, then the settings would be different for movies versus video-based TV shows, for example.