Two Photos libraries on iPad with Photos app?

Your iPad (and associated Apple Account) has just one Photo Library - however, you can have multiple Photo Albums within your Photo Library.

The (often overlooked) iPad User Guide is a rich source of information. Here are two direct links to relevant sections of the Guide to get you started:

Browse your photo library on iPad - Apple Support

Create and work with photo albums on iPad - Apple Support

You are very welcome.

Unlike your Mac that supports multiple user accounts, iPad and iPhone are essentially single-user devices. The Apple ecosystem is consistent in that each user (i.e. Apple Account) has a specific set of resources, such as a Photo Library, that is maintained on a device that in most instances are synchronised with iCloud.

The Mac's ability to have multiple photo libraries is not tied to the creation of multiple user accounts. You can have multiple Mac Photos libraries that belong to a single user. Only the one designated as the system Photos library can, optionally, be synchronized with iCloud Photos. The others are strictly local.

Likewise for Music and TV libraries, although I'm not sure how the Finder decides which ones to use for manual synchronization if there are several of those. ("Currently selected"?)

Create additional photo libraries in Photos on Mac - Apple Support

Use multiple libraries in Music on Mac - Apple Support

Use multiple libraries in the Apple TV app on Mac - Apple Support

I would guess that one reason that the iPhone and iPad support only a single instance of each type of library is to simplify the user interface. Another might be that iCloud Photos is positioned as a sort of "backup" for an iPhone or iPad's photos, and iCloud itself currently does not have a concept of multiple Photos libraries.