Is it possible to stream/cast my photos app running on my iPhone to an iPad to have a larger screen to browse my photos? I don't want to move or copy them to the iPad, I just want to access the iPad's larger screen to review photos and delete the poor photos from a group. Is there any capability to do that much like AirPlay can handoff to a TV, can I likewise handoff to an iPad? Alternatively can I mirror my iPhone screen to an iPad?
I don't think there is a native option here. You cannot use the iPad as an AirPlay target. Maybe there is a third-party app? I have two options for you that may or may not help, as they are not exactly what you asked for.
Option 1 (iCloud - Photos app)
Your easiest and most "Apple way" would be to use the Photos app in combination with iCloud to sync the photos between the two devices. You can edit them on the iPad and these changes get made on the iPhone as well. You can also delete them, sort them and do whatever you want with them, the changes will be synced to your Phone and vice versa.
The Photos app is smart enough not to fill up your storage and only keep some photos locally if you don't need all of them. (You will see them all, but they may take some time to download once you click on them depending on your internet speed)
Option 2 (AirDrop - copy paste & copy paste back)
Another option would be to AirDrop the photos to the iPhone, edit them there, and AirDrop them back. This would not match your request that you "don't want to move or copy them to the iPad". But it is an option that is fast and does not require iCloud.