There are some areas in Cape Town where I would try to avoid walking the streets at night/after dark. Daytime there is no issue. In the CBD/City Bowl there are a lot of homeless people/beggars on the street that will ask you for money or to buy them food. I didn't feel unsafe but the number of strangers approaching you is too much. Uber is very popular and rates are cheap. But in general Cape Town is a lovely city and certainly recommended.
English is spoken everywhere. No issue at all.
I'm not into your kind of guys, sorry, so I don't have any first hand experience and I wasn't looking for twinks. I didn't notice any on the apps.