At how many #users, NPS matters?

I am building Pearmock. There are 185+ product managers from all over the world practising product problems and earning points for doing the same.

It has been a few weeks since we went live and have reached organically to 185+ PMs. The question I have is at what point should I roll out a NPS survey?

Should I wait for the #users to cross 500 or start tracking metrics like NPS? one thing I am thinking is that at this point, I can also directly talk to users to get to know if they are happy with the product.

Would like to know your thoughts. The address is https://pearmock.com