Equal risk... Essentially, there's always a risk you can enter the US and stay with your significant one, whether you have K-1 or CR-1 pending or no cases pending at all. But, if any petition is filed, I *believe* CBP can see it in their system. They can always ask whether you know anybody in the US etc and you have to answer truthfully. If you lie, that could be a misrepesentation, which is an issue for becoming a lawful resident or getting other visas.
However... This forum knows many examples when people with pending K-1 or CR-1 visited and left just fine.
If you want a definite answer - I cannot give unfortunately. There's a lot of discretion by CBP, when you enter the US. A person may be in a bad mood and deny somebody, that's not that rare.