1) you cannot disable password request at the boot <- your disk is encrypted and OS cannot continue without the decrypting. It is not similar to disable the password request while entering KDE or GNOME, while in this case the system is running giving you a chance to login your preffered user automaticaly by inserting your saved credentials....
Yes, the boot partition remain unencrypted. In practice looking at my disk you have three partitions:
sda1 (/boot/efi, obviously the GPT boot partition)
sda2 (/boot, the linux kernel)
sda3 (holds the encrypted volume)
The whole thing remains safe, because UEFI by design checks that the contents of /boot/efi are unaltered, and these can check the contents ...