When using the new Photos app in Windows to view photos, the mouse wheel will zoom in and out of the current photo instead of cycling through different ones in the collection.
This can be changed if needed. Here is how:
Open the Photos app and click on the dots icon at the top-right.
Then select Settings from the drop-down menu.
From the Viewing and Editing section, scroll down to the Mouse wheel section. The default option selected here will be Zoom in and out. Instead, change it to View the next or previous item.
So, from now on, you can use the mouse wheel to view the previous or next photo in the collection.
Also, just like the Mail and Calendar app, the Photos app too now supports dark mode. To enable it, from the Viewing and Editing section, scroll down to the Appearance section.
Change the mode to Dark. For this change to take effect, close and reopen the Photos app.