By canon Rayleigh gets Shakky.
Even if Ray not the person to rescue Shakky, her heart still belongs to Ray.....so she'll go back to Ray in the end.
If they fought and who wins?? Then nobody.
Garling won't be defeated or look pressured i guess, this dude is unhinged, never show extreme emotions or "negative" reaction everytime he's onscreen.
Garling got the Aura that is legit untouched. He's the perfect guy that is the definition of "saving up for later"
And not a chance in hell would he look bad in a flashback when we don't know shit about his capabilities but all we know is he got a solid portrayal + he's obviously going to be one of the big bad boss in the future arcs or EOS.
Rather being outshined by Rayleigh..... Garling have a big fat chance to look better than even fking Rocks, Roger and Garp in this flashback due to his future relevancy and portrayal as Imu #2.
And i doubt Ray would be mistreated or took some L in this flashback. So neither can look bad, so Ray most likely snatch Shakky during the time of chaos all over the place.