Admittedly I haven’t been on for the past two weeks when it was implemented, so it’s hard to tell whether there’s been more posts from new users resulting from the changes.* Maybe those are stats that the admins might have access to, or not at all.
*If there are, I’m curious how they’ve discovered this place.
Agreed, the booru-style filter for default view would be good if it exists in the future. I think RA2lover’s suggestions of non-auto expand and blurred thumbnails for NSFW posts would line up with your “disable auto-expand posts from more extreme communities.” Might be hard to get agreement or to draw a line in the sand and say “This is extreme and this isn’t”, so if it comes to that I’m in favor of erring on the side of caution and non-auto expanding + blurring all NSFW posts for the visitor view (since these posts aren’t gated behind logins). And tailoring the CW popup is a great idea as well, though I’m not sure whether mention should be made of the more extreme content at the pop-up or left for them to discover upon actually hitting the site.