/dev/input/mouse0 or whatever number you may have if for some reason you have more of them. Plus the always present /dev/input/mice shared between all mouse devices.

Computer mouse or live mouse? Yes

Straight to file.

you are correct, directories are 4kb files

Logically, everything stored to disc is a file. There are no physical folds or branching on a harddrive's platter. Everything is (this is simplified) listed one at a time, end to end sequentially. A directory is just a special text file that lists all the addresses to files that are logically "inside of it".

With journaling file systems (aka modern file systems), this is either replaced or superceeded by the journal.

Moreso, in Linux, most things are also logically treated as files. In Windows, some settings are stored in a special database known as the registry--Linux has not. It just has text files. In windows, devices are in the device manager, in Linux, devices are just another directory. In Windows you have a special task manager to view open processes, in Linux we have /proc which is a virtual directory. Windows: user permissions are managed with the active directory application. Linux: file permissions. etc.

This means, instead of using special apps to view things, you can, if so inclined, just navigate and look at files using the usual terminal.