I think Gohan would win without Kaio-ken, since you can't mix Kaio-Ken with Super Saiyan unless you're dead.

A total X1200(400 x 3) multiplier? Yeah he's reverting back to base instantly. SSJ3 already has a ki drain issue and Kaioken on top of normal SSJ still puts heavy strain on the body, it's why it worked only when Goku was dead, or when it was combined with the calming ki control of God Ki.

I see Future Gohan doing damage, but I feel like that much strain on him is not gonna be worth it.

^^You can, but it'd be hella stressful and painful on your body.

Too much strain so I doubt Gohan wins this, without kaioken he has a much better chance