How can I quickly add a photo to an album in Photos app?
I'm assuming you're talking about the Photos app on Mac.

One option based on your description is to change the size of your thumbnail images so they're large enough to view the quality of images without having to manually open them up one by one. To change the thumbnail size drag the slider near the top left of the Photos app window.

Once you've got the size right, you can select multiple images (using the Command key) and then drag them across to the album you want. Of course, this assumes you've already created the album. 

Another option, once you've selected the images you want, is to then go to File > New Album (or just use the CommandN keyboard shortcut) and this will automatically create a new album including all the photos you had selected.

If you're interested in the full list of keyboard shortcuts for the Photos app, just go to Help > Keyboard Shortcuts. This will give you quick access to a list of keyboard shortcuts as well as Magic Mouse or trackpad gestures.

Hope this helps!