Yes, the first screen you see with the function keys is the Splash Screen
The BBS options, or BIOS Boot Specification (your semi-opened books), has existed for a while. They are what might be called boot profiles, vaguely similar to a BIOS/UEFI profile. The BBS settings allow you to create several different boot orders, and boot orders for different boot devices. One sets the order for hard disk drives, another for optical/CD/DVD drives. You also have network boot devices, Ethernet cards or onboard chips, and detachable devices like USB flash drives. It's a bit much for most users, but can come in handy for advanced users, really a convenience, rather than setting boot orders specifically every time you need to do something different.
UEFI and AHCI are not related in the respect you implied. While a UEFI boot device must be formatted in the newer GPT format, AHCI is a SATA I/O protocol, that would still be used with GPT formatted disks. It becomes complicated at this point with UEFI, and has more to it than I am willing to type in, or completely understand. Most people do not use the full capabilities of a "UEFI boot", beyond the UEFI type of BIOS. Many people consider the GPT disk format type to be a failure, or overly complex for no return. It can be necessary for very large HDDS, over three TeraBytes.
I cannot recommend something that I have never used, or completely understand, which is what true UEFI booting and disk formatting is to me.