RF amplifier top level design
The devil is in the details.  To the degree that the two amplifiers are matched and the phase splitters &amp; combiners match up, you should be able to reduce the 2nd-order effects nicely -- but "nicely" means something like 10 or 20dB.

You won't change the 3rd-order performance much, unless each amplifier ends up running at half power and if the amplifiers perform well at half power.

And don't be surprised if you build a push-pull power oscillator, or make matters worse -- your scheme depends on good isolation between the amplifiers.