The new default bootloader being systemd-boot, it needs the ESP to be mounted at /efi.
Also, if I am not mistaken, the default size for it is 1000 MB since it will house your kernel images.
It you would opt for Grub, instead, the previous recommendation to mount it at /boot/efi is still valid.
Yes. To my knowledge, if you have both Windows and EnOS on the same disk, then an entry for booting your Windows via systemd-boot menu will be created automatically.
If you have them on separate disks, you would need to take some steps yourself to add Windows boot entry.
See: [Tutorial] Add a systemd-boot loader Menu entry for a Windows installation using a separate ESP Partition