You will be shown a preview of what your merged library will look like before any modifications are done, to ensure your merged library looks how you want.
It's easy to have multiple copies of the same photo creep into your photo collection over time.
Power Photos works with the built-in Photos app on your Mac, providing an array of tools to help you get your photo collection in order.
Instead of being limited to putting all your photos in a single library, Power Photos can work with multiple Photos libraries, giving you many more options for how to organize your ever growing photo collection.
Keep your Photos library and Time Machine backups on different disks.
An easy way to do this is to keep your Photos library in your Pictures folder (the default location), and set Time Machine to back up to an external drive, a disk on your network, or a Time Capsule.
If two or more users attempt to use the same library and the library isn't on a volume where ownership is ignored, you might see unexpected results.