If I opted for referenced photos while importing images to Photos, would adding new photos to a Finder folder get updated into Photos
No. Photos does not have a 'watched folder' capability. You would move your images to your preferred location and afterwards import them to Photos. Deleting is the inverse. First you delete them in Photos and afterwards go to your folders are remove the image. It's these kinds of inconveniences, allied with the lack of any actual file management tools, and poor ability to reconnect with lost images are among the many reasons that experienced users do not recommend using Photos in that mode. There is no actual advantage to using a referenced library and many disadvantages. If you really want to use a referenced library I would urge you to find a different app, one with the tools you need for the job.
Assuming the Photos folder/album structure would match the one in Finder.
This could never happen. Folders in Photos only contain Albums or other folders. They do not contain images. Folders in the Finder contains actual files as well as other folders. The Finder has no concept of Albums.