Manjaro Double Install With Itself

Hi guys,
I was trying a double Manjaro install into the same disk (different partitions) with grub to manage the dual boot. I was unable to do this straight on because there’s eventually some kind of overwriting of files in the /boot/efi partition. The hardware is configured this way:

/dev/sda1 /boot/efi
/dev/sda2 / for manjaro 1
/dev/sda3 / for manjaro 2

Any thoughts about the best and simplest way to achieve this goal? I really don’t like to have different DEs on the same install so I prefer to duplicate the install. This is the main reason to double install Manjaro.

I hadn’t to many problems with multiple DE, but i have read recently the recommendation of running a different user for each DE. Would that perhaps solve your problem?

Wouldn’t it work to install the first one, then the second, followed by booting the live ISO, doing a manjaro-chroot into the first installation’s environment, and the reinstalling and recofiguring its grub?