Since this is all confusing it would be way easier if you mention what ticket class and your status since some choices might not be available to you.

I think that you have to read through the interim 772 map thread to see what seat selection in the 3-class 772 will give you the best seat in the Polarized plane for your ticketed class if a swap occurs.

This is the thread for if your flight remains in the original configuration.

There is a thread "Everything you want to know about where to sit on a 777-200 v5/Polaris seats/77J which gives indications for if you fly Polaris Business but it does not have correct indications as it does not show the Premium Plus seats for if you fly Economy (and the seat numbers are incorrect)

There's a thread about the 777-300 ER that also gives good indications for Polaris Business seat selection. Odd windows are the best for privacy.

Maybe you should try Googling with the key words being FlyerTalk and United and where to sit.....