What is the difference between /dev/usb, /proc/bus/usb and /sys/bus/usb?

Take from the wikipedia:

/dev Essential devices, e.g., /dev/null.

/proc Virtual filesystem documenting kernel and process status as text files, e.g., uptime, network. In Linux, corresponds to a procfs mount.

/sys Modern Linux distributions include a /sys directory as a virtual filesystem (sysfs, comparable to /proc, which is a procfs), which stores and allows modification of the devices connected to the system, whereas many traditional UNIX and Unix-like operating systems use /sys as a symbolic link to the kernel source tree

as also mentioned https://su/q/alternative-to-proc-bus-usb-devices, /proc/bus/usb/devices is deprecated. see Kconfig documentation.