Create a Smart Album with the condition Photo is referenced. then you can select all images in that Smart Album and use File | Consolidate.
I’ve found that if you select a group of images in Library and try to consolidate, Photos is sensible enough to work out which ones are referenced or not, but for some reason if you try to select all images and consolidate, then File | Consolidate is greyed out and unavailable. Thus using the Smart Album to find them first is best.
You can, however, select all images in Imports and consolidate, but that may not represent all the referenced images at that moment. The Import view only seems to go back so far.
As to assigning keywords, Photos isn’t the best tool, but it’s usable. Select the images you want, then ⌘-I to open the Info window, then you can enter a keyword for them all in one go.
Also, look into the Keywords window – ⌘-K, which shows you all the keywords for all images in the Library and highlights the keywords for the currently selected image(s).
Info correct as of macOS 14.4.