Verbose boot is nothing like "superuser". Verbose just means it'll giver "verbose" output when booting; I.e. print every step of the booting process to the screen. It's like turning on normally except with extra log messages. Single user mode boots only partially, then gives you a command prompt as soon as the system is ready to spawn a prompt, but before it's ready to facilitate full macOS, so you can poke around in things that you can't poke around with in a fully running system. Very rarely needed, but helpful to have as an option; Most the time just using sudo in a Terminal will give you enough "super user" access though