What are your thoughts on previewing passages (not questions, but just looking at each passage for a few seconds) and trying to do them in order of difficulty? Do you find that it wastes or saves time?
I think this depends on how you feel regarding timing on the exam. If timing isn't an issue for you, then I wouldn't preview passages and just work my way through everything. However, if you find that you're really struggling with finishing sections on time, then I would spend a minute or two triaging and doing the easier passages first so you don't end up wasting unnecessary amounts of time on harder passages.
IMO, for every passage, take as much time as you need (4-6 minutes) to understand the flow of the passage. If you’re previewing passages to gauge difficulty, then I wouldn’t recommend it since you’re wasting time that you could be using to understand the passage better. If you’re previewing the passage to see the overall flow and main theme, then go for it.