Parameter types for Track.insertClip and Track.overwriteClip?

What are the parameters for the Track.insertClip and Track.overwriteClip functions? Specifically I'm interested in understanding what parameters are allowed, what parameters are optional, parameter types, and the return value, if any, of the functions.

Here's what I've been able to glean [in TypeScript format] from the Premiere.jsx examples:

// insertClip's second parameter can be either a number or a string.

insertClip(clipToInsert: ProjectItem, timeInSeconds: number): void;

insertClip(clipToInsert: ProjectItem, time: string): void;

// overwriteClip only has a single example (using a number for the

//  time).Does it also accept a string?

overwriteClip(clipToWrite: ProjectItem, time: number): void;

The stuff I'm unsure of is colored red.

Further, any documentation about what the APIs actually do would be very useful. For instance, if the time specified for overwriteClip is in the middle of another clip on the Track, does the entire clip get erased and the current clip inserted at the specified location, or is the existing clip get truncated at the point specified before insertion?

Thanks!