I don't actually use Reddit or Twitter, but I sometimes come across NSFW posts from links. I've found that old.reddit.com seems to allow you to bypass the filter(s) without needing an account. For Twitter, I tend to use the xcancel.com Nitter instance, though there are other Nitter instances that work fine.

Bonus for using Nitter here, you can also see the latest posts from an account instead of the most popular posts, and see replies/interactions to individual tweets. Oh, and it gives you plain HTML.

Reddit pisses me off so much that despite the fact that I don't even use Reddit, just so that my experience sucks less when I'm linked to Reddit or have another reason to lurk it,

- I use the "Old Reddit Redirect" extension to force the browser to go to old reddit

- I use the "Load Reddit Images Directly" extension to bypass Reddit's hideous image viewer that tries to load if your browser makes the mistake of having text/html in the "Accept" headers when opening an image in a new tab. (Dear Firefox/Chrome/etc: maybe stop doing that? If I open an image in a new tab, there is a zero percent chance I want HTML.)