If you select the GPT style for the USB drive, FAT32 and NTFS file systems are offered.Then, the USB drive can be used to boot BIOS-based PCs only.

If you select the MBR style for the USB drive, only the NTFS file system is offered.You can download a Windows ISO file and then use a burning program to burn the ISO file into the USB drive. Then, you can use this USB drive to boot either BIOS-based or UEFI-based PCs. If the USB drive is larger than 32GB, it will create a 32GB FAT32 partition and leave other space unallocated.

If you use this method, you don’t need to care about the USB format because the Windows Media Creation Tool will initialize the USB drive to MBR and then reformat it to FAT32 automatically when it creates the installation USB drive. To get the detailed steps, you can refer to this post: A Complete Guide to Windows 10 Media Creation Tool: How to Use. Insert a USB drive into your PC, run the MediaCreationTool22H2.exe tool, and follow the wizard to create a Windows installation USB drive. You can get it from the Microsoft Windows 10 Download page.

To understand the effect of USB format on PC booting, you need to know how to create a Windows installation media. Read More How to Create a Windows Installation Media?

Format a usb drive to fat32 windows 10