Does that means that I won't be able to see pre-offers if I visit credit card websites?
If you have an account with a creditor they can still SP with a freeze in place.
I believe when you freeze your credit reports they put you on a list for something like 5 years where they wont give your info out thus probably no mailers.
I think you're conflating a freeze with opting out. A freeze prevents pulls of your reports unless authorized. The opt out site allows you to opt out for 5 years, permanently and opt in,