The Brainiacs should take it. B1 is easily physically powerful enough to take on Kal one-on-one, and while B8 never really fought herald levelers, she did take, in order: Grace, Shift (the Metamorpho clone), Jade, Thunder, and Starfire, all with little effort. In the end the only reason she was taken down was 'Indigo' temporarily gained control to give them a chance.
The Superman: Brainiac TBP had them physically confront each other and iirc Superman did not have an easy time of it, B1 was at *least* as powerful as him if not better.
Brainiac's cyborg body is surprisingly badass.
This is, btw, a downgrade from his really early appearances, where he pretty much yawned through Superman's attacks.
There are lesser versions of Brainiac post-crisis, like the human with mind-control powers, but those are basically probes of the true Brainiac and not the real deal.
B8 hasn't shown as much physical strength, but has shown greater versatility in her built-in capabilities, with powerful forcefields, rapid self-repair, high-level sonics, and so on.
Again, where are you getting that? You haven't read the fight and don't know his capabilities.
His latest, and officially 'true' body fought Superman once and dominated most of it. Brainiac was simply written stronger, and through the rather logical method of a 12th level intellect constructing itself the most powerful body available.
She has other powers. High-power blasts? Force fields to defend her ancestor while he attacks? High strength herself? (and enough self-repair to come back in short order even if her arms are ripped off) All will aid in the beat down.
Or her analytical abilities- I wonder how long it'd take her to figure out how to do something with his gamma radiation considering she was able to figure out how to cancel GL energy.