grub-efi bootloader & windows 10

[thufir]

How does the grub-efi bootloader indicate that it's in EFI mode and not 
MBR?

Reading:

http://askubuntu.com/questions/395879/

the simplest answer to create a UEFI bootable thumb drive is like:

7z x ubuntu-12.04-desktop-amd64.iso -o/media/$USER/604A-00EA/


This is to dual-boot with Windows 10.  I've looked at some different 
sources but don't quite follow how the ESP fits in to the picture.  This:

"Note that these factors can conflict with one another. For instance, if 
you're dual-booting with a pre-installed Windows 8 but have problems 
getting a UEFI version of GRUB to work..."

https://help.ubuntu.com/community/UEFI


doesn't put me at ease.  In the firmware I'll disable QuickBoot/FastBoot 
and Intel Smart Response Technology (SRT) as per the the fine manual and 
will use the EFI image as described above. 

Leave the firmware in UEFI mode and don't switch to Legacy?

I'll "try Ubuntu without installing" to boot to a live system.  I want to 
use the grub-efi bootloader and will do the echo test as:

[ -d /sys/firmware/efi ] && echo "Installed in UEFI mode" || echo 
"Installed in Legacy mode" 

but before I do the echo test, how can I _ensure_ that the grub-efi 
bootloader installed to the ESP (?) so that it plays nicely with Windows 
10.


thanks,

Thufir