Can't change screen resolution of Android-x86_64 installed in UEFI mode
I got it.

Short answer: This line should go in the bootloader for UEFI mode:

set gfxpayload=1280x720


Explanation:


  On x86 systems, the kernel will be booted using the 32-bit boot
  protocol. Note that this means that the ‘vga=’ boot option will not
  work; if you want to set a special video mode, you will need to use
  GRUB commands such as set gfxpayload=1024x768 or set
  gfxpayload=keep (to keep the same mode as used in GRUB) instead.
  (...) The linux16 command (see linux16) avoids this restriction.
  
  GNU GRUB Manual 2.02: linux


See also, How Do You Pass VGA/VESA Modes with GRUB2? (Unix.SE).