Re the second point, I've examined the options, both by myself and with people from Apple Support (while screen sharing) and there doesn't seem to be any way of viewing just the photos taken using this iPhone (or even the photos taken using this iPhone, mixed together with photos saved to this iPhone). It's a very strange omission: one can choose to view the photos saved to this iPhone (via Recently Saved) or all photos but not the photos taken using this iPhone.In the pinned collections, there is a folder called Recently Saved. Could that be what you are looking for?
Also, if you scroll all the way down, there is an option to customize and reorder. Perhaps something in this menu could be helpful for what you are trying to do?