H&Cs are intended to be decided upon the consideration of all of the factors included in the application that are relevant to the department's policies, and credibility is an underlying aspect of any application. The H&C decision-maker doesn't have to rely upon the finding of an earlier decision-maker but they can reference that finding as they assess the general credibility of the H&C application themselves.
In other words, the person deciding the H&C can see what the RPD decided and accept or ignore it as they look through the other material relating to establishment, children, the support from whomever and all of the things unrelated to the refugee claim and any risk of return. You don't earn any points for a lack of credibility but it doesn't immediately end the H&C for you. Having said that, if you have serious credibility issues - where you just cannot be believed - then that's unlikely to end well because a history of misrepresenting facts means you cannot be taken seriously.
There is nothing extraordinary for an H&C decision-maker to see a failed refugee claim where credibility was the issue so let's hope your other factors work for you.