A:AnswerYes you can have multiple screens. I bought a plugable 3.0 docking station and have two monitors connected. But you can have single monitor connected. The only issue is that the laptop only has C ports. Not sure about the photo shop program.
A:AnswerThere are two USB C and one thunderbolt I/O ports. Try adding the Samsung HDMI adapter to both USB C ports, the only issue may be assigning the display in settings.
A:AnswerMost likely not, this is not a gaming laptop and does not have a dedicated GPU and instead runs off intel Iris graphics. Unless you want to buy a Thunderbolt 3 external GPU enclosure like the Razer Core X.
A:AnswerI'm not sure if this would help but I have my adobe creative cloud that includes all the apps on it and I constantly run photoshop and lightroom without a problem.