About question no. 2
Android:
You can compile your app using Crosswalk = you can use native AdMob ads, but your game will jitter
You can compile your app using CocoonJS = game will not jitter (or jitter much less) but you can't use native AdMob, only MoPub (so you will earn 70*% less due to low fill rates and low eCPM)
iOS:
You can compile your app using CocoonJS and get amazing perfomance, however CocoonJS still uses MoPub, so you will earn 70%* less on ads (comparing to native ads)
So we are still waiting for ludei to implement native AdMob ads
and we are still waiting for not jittering Crosswalk IntelRobert
Of course you can still make super advanced 1 screen game and compile it with Crosswalk, and hope that jittering won't be visible.
* - at least