The Photography plan is both Photoshop and Lightroom.
Photoshop alone is $20/month.
The Creative Cloud Photography Plan (Photoshop + Lightroom) is $10/month and a much better deal.
Does Photography Plan include all the fonts accessible in Photoshop, or is it watered down?
There's nothing watered down about the Photography Plan other than the price.
It's got the exact same version of Photoshop.
Seems like the lower price makes people suspect there's a catch but, in this case, there is not.
The Photography Plan comes with Typekit Trial while the Photoshop Single-App Plan comes with Typekit Portfolio.
Desktop Fonts: Choose from 130+ fonts
20 fonts synced at once
Web Fonts: Choose from 800
2 fonts per site
Desktop Fonts: Choose from 1000+
100 fonts synced at once
Web: Choose from 4200+ fonts
Unlimited fonts per site
If that many fonts are missing, can fonts be imported or will I be stuck with the limited number?
Yes there is a difference with the Typekit plans available.
Photography Plan subscribers generally don't need Typekit.
If Typekit is important to you then you'll need either the Photoshop Single App plan or upgrade the Typekit trial which comes with the Photography Plan (and pay for that separately).