If you would like to boot your client using UEFI, you need to select ”UEFI x86_64”. The architecture will automaticall be set to 64bit, as m23 only supports UEFI for 64bit systems. If your client computer does not support network boot in UEFI mode, you can use the 64bit boot ISO (see menu item ”Create boot media”).
Bootloader: Choose the boot loader/boot manager for starting the Linux kernel and possibly already installed other operating systems.