The Dell monitor that you list supports 1920x1080 HD - this being the minimum supported resolution for the iPadOS16 Stage Manager feature.
You should note that while theoretically compatible with your iPad, supporting DisplayPort 1.2 over USB-C, this HD monitor has a lower effective resolution (1920x1080 at 158 ppi) than your iPad screen (2732x2048 resolution at 264 ppi).
As such, when mirroring your iPad screen, the image will not be as sharp - and when used with Stage Manager, may be a limiting factor in the relative usefulness of the Stage Manager windowed environment.
A slightly larger 4K Portable monitor might be considerably more flexible in its usefulness. By example, a 15.6” 4K UHD monitor will provide 3840x2160 resolution at ~280ppi - this being a similar pixel density (and hence image sharpness) to that of your iPad.