I don't know what computer you have but I use a Mac mini. I put an external drive on it and use reference pointing for Photos. So the photos are not actually stored in Photos app, but a reference pointer to the physical file located on the external drive. This way I can store all my photos in folders (by year/month) and only add select photos to my Photos app (curated).
Photos can store its library anywhere. Mine is on an external drive. All you need to do is hold down the option key when you open Photos and tell it where the library is. This only needs to be done once.
Moving the Photos Library to the external is probably the better way. With a referenced Library, there's always the possibility of accidentally deleted the originals on the external, and then Photos can't find the picture.