1280x720 for Handy is ok, but full hd is better for pc monitors.
also think before u make game art if you want use zoom in screen.
i have a 4:3 tablet but i choose more 16:9.
i using mainly screen buttons because android<>pc,
i want have something that can be used at all devices.
with the hardware keys i trigger my "screen" buttons.
i know that android supports switch to full screen, but don't know if it is possible
with agkv2 now.
if u useing square background (max width/height) or tile background
there is no problem.
AGK 108 (B)19 + AppGameKit V2 Alpha .. : Windows 8.1 Pro 64 Bit : AMD Radeon R7 265 : Mac mini OS X 10.10 (Yosemite)