How specific should you be in the nikah contract?

You should be specific enough to avoid dispute, not so specific that it becomes almost impossible to implement.

For example, there is nikah contract template that's floating around out there that's like 50 pages long.

There's so much in it that it is literally unenforceable. So there is overdrafting in legal documents, and you can try to put too much, and that'll actually be undecidable in the end of the day

So, you should put enough to where you can avoid the most major disagreements, and you have general principles to go back to if those aren't covered by specifics.

One way that you can avoid overdrafting, but also protect yourself is by mandating that there be alternative dispute resolutions and saying that you'll go to XYZ people as mediators that you trust that will be able to walk you through any disputes in a way that's equitable.