Help me get along with GPT/EFI please! :)

Hey, i got a new laptop which is set to EFI/GPT as stock. I set BIOS to legacy & format to MBR but i wanna learn. My problem is i usually use winsetupfrom usb to make bootable flashdrives containing multiple windows, linux, tools.. I can't find good information about using winsetupfrom with GPT partitions.

I actually don't even know how to make an EFI partition first manually. If i use RUFUS, i can create a bootable windows install flashdrive BUT this is JUST 1 windows. I'd like to go further and split the flashdrive in two partitions, second would be macOS installer.

I did this years ago & it was working good, however this was MBR. With the flashdrive formated by RUFUS, the EFI partition is few KB, which macOS (format utility) reject. I do not understand well how to change EFI partition size, especially here it's listed FAT12?!

You should leave your BIOS as EFI, not legacy.
As Win 7 isn't compatible with Secure boot, you must disable it and enable CSM (Compatible System Mode). And disable fast boot to be able to launch boot menu.

On a Legacy - MBR, BIOS takes to MBR, a disk sector that has the information where is the master boot loader.
If you have more than a OS in the disk, this Master Boot loader can have a option to take the sequence to another boot loader.
On a Legacy - MBR you choose a disk to boot from. Boot loaders are on a serial sequence, one after the other.

On a UEFI - GPT, BIOS takes to a EFI (100M- Fat32) partition where you can have many boot loaders.
On a UEFI - GPT you choose what boot loader to use on the EFI partition.

So if you want to use a USB flash disk with many boot able options, EFI is the best option.

Thanks for these explanations but i still do not how to proceed to create my flash drive..

I wish someone could help me here.. :=

Thanks but these didn't do. I found out an app called YUMI which helped! Perhaps it'll help someone here too