Assuming that he has enough self control or can give her the same super serum he gave Lois in All-Star Superman the answer is Lana.
I think there is any number of logical preventative measures against bone pulverization of a normal human woman that don't incorporate weakening superman.

Lana plays the role of confidant since she is one of the few who knows both of his identities outside his parents or select leaguers.

She is also the childhood friend and that makes her the top tier waifu.

Lois is the Tsundere.

Cat Grant is the slut.

Kara is basically the little sister.

Wondy is either the stoic and or the sporty girl.

I really want a Superman dating sim visual novel thing is what I'm saying.
A teenage superman going to Metropolis High or some stupid shit.