If I get the "easier" second module in Math, can I still get a perfect score of 800?
No. Because the test is module-adaptive, if your performance in the first module triggers the "easier" version of the second module, your maximum possible score is capped at a lower level. You must perform well in the first module to access the "harder" questions and the highest score range.
Are the Reading passages still long essays like they were on the old paper SAT?
No. The Digital SAT uses short "discreet" passages. Each question has its own individual paragraph (roughly 25–150 words). You no longer have to read a 700-word essay and answer 10 questions about it.
Can I use my own physical graphing calculator, or must I use the built-in Desmos one?
You are allowed to bring an approved physical calculator if you prefer the tactile feel. However, the built-in Desmos calculator is highly recommended as it is integrated directly into the testing screen and can solve many complex problems very quickly.