Understanding Grub2

[Richard Owlett]

Underlying motivation:
  I find how Debian uses Grub has _petty_ annoyances.
Historical background:
  When asking questions in past the response was "OS specific".
Tentative project description:
  "A *MINIMALIST* install of a pure GNU GRUB system"
Underlying assumption:
  I have a lot of reading ahead.
  (https://www.gnu.org/software/grub/manual/grub/grub.html does
   not address my questions. Or if it does I don't see it ;/)

My hardware can boot from a USB connected device and a MBR BIOS is used.
I wish to dedicate the first partition to Grub and an absolutely minimal 
set of Linux core components. The result will be able to run on any i386 
machine capable of booting from an external device. As there may or may 
not be a complete OS elsewhere on my device, it implies the functional 
equivalent of "update-grub" being on same partition to which the 
minimalist Grub has been installed.

I've accomplished something similar on my working machine by doing a 
complete Debian install to /dev/sda1 and when making further Debian 
installs to /dev/sdaN choosing to install neither LILO nor GRUB.
["update-grub" present ONLY on /dev/sda1]

Comments/Suggestions?

TIA