WhatsApp read receipt if number is not saved?

Hey everyone!

Can you turn read receipts on in WhatsApp for saved contacts and off for unsaved contacts? Or does it make no difference between saved and unsaved contacts if you turn read receipts on or off?

I also have a question: if you turn off read receipts and then turn them back on, will all WhatsApp users you chat with privately be shown that previous messages have been read? Or will they simply remain unread?

Thanks in advance!

LG