I did a little bit of investigation into how Apple Photo's works this week. I wanted to make "public" photo albums and turns out there's 2 ways to do this.
Firstly, you can share a normal photo album and get a link for it. To access this on a Mac you go to the share icon > "Copy iCloud Link" from the album. You end up getting a link that you can then access for a month.
If you want a link that never expires and is a public album you need to created a Shared Album. You then click on the little face icon from the shared album and make sure the "Public Website" checkbox is checked. You then end up with an album like this.
So I guess for viewing photos a Shared Album is better but for bulk downloading images and sharing them a normal album is better.