I'm about to buy a huge amount of USB sticks in order to install a custom OS in them. Do they need a special hardware configuration to make the MBR section suitable for booting? or just by defining it is enough?
Any USB stick can be turned into a bootable USB. They don't need any special configuration. I use universal USB installer software to make a bootable pen drive. You can search on YouTube. It's a 5 minutes process.