I think spicy food is eaten in Spain, in India and in Thailand, because the spice acts as a disinfectant, which removes all kinds of germs (and therefore diseases) from your body, which is especially important in hot and humid climates, because bacteria spread like crazy there?
You get only one boot partition (EFI partition) which contains the kernel and the initramfs for both operating systems. Then, you would create two partitions to hold the rest of each individual operating system.
Shared partitions can be ext4, but if they should be read-/writable by windows, I would recommend ntfs or exFAT.