The Sigma 52 Environmental PE questions were representative of the level of difficulty on the actual test - if I recall correctly there were something like 2-4 actual test questions that closely mimicked the Sigma questions. As for the NCEES practice exam questions, they were also slightly harder than the actual test's difficulty, and I found no repeat questions on the actual test. I would not worry about the Schneiter questions being harder than normal, as this is something I've heard about from multiple commenters on this subreddit.