How would I get the time of a playable when it is running? For example, how would I execute some code if the playable if currently at 5 seconds?
You could use animation events, or use IEnumerators in your code to wait the desired amount of time before executing the code. Here is a tutorial for learning IEnumerators: How to Coroutine in Unity | Unity Beginner Tutorial - YouTube
The answer depends mostly on what kind of code you want to run I guess.
You can use animation events. You can use signals, or you can just put code in PrepareFrame or ProcessFrame which checks the current time and calls functions when appropriate.
Animation events and signals are purpose-built to execute code at a given time, so you should start with one of these before you build a new playable, as getting this right is trickier than you may think.