if you go to the Kickstarter page for Luna it seems that the Luna app it self will not have the same controls for creative tools like those found in Astropad basic and studio, the Luna app is more like Duet Display from what I can see its just allows the iPad to act like a second display with touch, but you will yes still be able to use photoshop tho I don’t know if pressure sensitivity will be useable.
If you read it it says:
“Luna fully integrates with our award-winning drawing software Astropad. Luna extends both Astropad Standard and Astropad Studio to provide the ultimate drawing experience with the best second screen solution for iPad. If you are a creative professional, Luna has been designed with you in mind.”
If I’m not wrong luna haves it own app witch dose not have the same creative controls as is Astropad Studio version but the Luna device it self still works with Astropad Studio. So if you like the addons within the studio version then that is why you would use it over the Luna App.
I don’t know if the Luna app haves all the same things within it compared to the basic version of Astropad tho.
I might be wrong completely and Luna may have all the same things within both basic and studio version of Astropad.