ventura turn off screen switching

I would say Stage Manager in Ventura may supply the desired effect to possible achieve this

refer to link below

Use Stage Manager to organize apps and windows on Mac

And or " Use Mission Control on your Mac "

refer to link below

Use Mission Control on your Mac - Apple Support (CA)

" my own chosen screen saver " sounds like the User has enable Hot Corners

refer to link below

Use hot corners on Mac

You can use the corners of the screen as hot corners, to quickly start actions when you move the pointer to a corner.

For example, you can start the screen saver when you move the pointer to the top-left corner of the screen, or lock the screen when you move the pointer to the top-right corner.

Tip: By default, the bottom-right hot corner is set to Quick Note, so you can quickly open a note to jot down your thoughts at any time. See Start a Quick Note.

1. On your Mac, choose Apple menu  > System Settings, then click Desktop & Dock  in the sidebar. (You may need to scroll down.)
2. Click Hot Corners on the right.
3. For each corner you want to use, click the pop-up menu, then choose an option, such as Notification Center, Launchpad, or Lock Screen.
4. To use a modifier key with the hot corner, press and hold the Command, Shift, Option, or Control key, or a combination of these keys, while viewing the pop-up menus.
5. Click Done.