I won't listen to a sales pitch that is under NDAs. But I also won't ask the seller to specify the solution for free.
Having some sort of agreement about IP, on the other hand, is possible but enforcing it would be costly any way. There's no easy solution.
When you are a small outfit, you cannot afford to work for free and you must make it perfectly clear to your prospects. If they can't respect that, you shouldn't try to serve them.
It's very easy to win a contract and then be completely crushed by your client. Believe me: I have seen it happen a couple times.