Douyin content is very similar to TikTok content. There are many popular douyin creators whose content gets copied to TikTok. There’s loads of makeup, cosplay, cooking, skit, DIY, etc. Mukbang style content is very popular there as well. Their makeup and fashion content, like on TikTok, is sponsored by huge international brands like Mac and Gucci and others along those lines. Also super popular is pet content, like people who run cat shelters and dog walkers and stuff. There is also no age verification to use the app unless you want to post or comment yourself, and there is no time limit to use it. Some TikTok creators get reposted to douyin as well, but the overwhelming majority of people in china do not speak English, and to post on it, you need to be a citizen of China. Not that there aren’t ways around it, but it’s harder than it’s worth.
I get that you’re paranoid about Chinese international political interference, rightfully so in some ways. But this is just blatant lies and fear mongering. I’ve used the app extensively myself to follow some makeup content creators from China. It’s functionally identical to TikTok. Censorship does exist, but it’s based around specific events, mostly from what i can tell. I don’t use to find political content, but I wouldn’t be surprised if they censored content based on stuff like the Honk Kong protests. Propaganda is also on there, most likely, but I never encounter it in my feed.
Pretty uncommonly, since you need a valid Chinese phone number to make a douyin account. A few english speakers living outside china get posted there, but English isn’t a super common language in mainland China. It’s there of course but not widespread enough for it to be much of a market for it. Not to mention America and China are culturally quite a ways apart and I’d imagine western content wouldn’t see widespread popularity there.