Chinese cabbage is an overall term for Oriental brassicas. some are leafy, some semi heading, and some like NAPA are full heading. You will have to adjust for your taste, but you can eat any of them at any stage.

Here is a link that might be useful: Chinese cabbage

It is "ok" to eat them if they are starting to bolt or actually have bolted. They are just as nutritious, they just start to get bitter. The more time goes by the more bitter they get. It depends on your tolerance for bitter-tasting things, or on the finickiness of the people you are feeding.

Cool fall temperatures keep it from getting bitter as well as allow them to grow much longer before they bolt.

Stir-fry it with some vinegar and garlic and/or hot sauce.

Sure, you can eat it. Flavor is slightly stronger as it bolts, but overall growing conditions probably are a bigger factor in flavor than bolting, bolted cabbage grown under cool, wet conditions still won't be that strong tasting.

Many Asian cuisines prefer various types of Asian brassicas bolted and specifically grow them to use at this stage. There is a large upscale produce market near me that caters to many ethnic clients, and they have various types of blooming bok choi, mustards, etc. for sale.