Coffee shop is very casual, just like when I go, I can stay there and read books by ordering a cup of coffee or something.

Chatting and writing can be done, generally there is no time limit.

Some coffee shops have refills, and there is no culture in China, but you can sit in Starbucks for hours without seeing it for a day. Generally speaking, the clerk won't kick you out, so Starbucks has no time limit. You can order a cup of coffee and sit for a day if you want.