Which cameras produce video that can be edited on a mac without transcoding?
One way is to ask the people in the shop you intend to buy from.
Or (if you plan to buy online), narrow down to a list of potential cameras then ask again here with specific camera names.

Another idea is, if you have a compatible memory card, go to shop, ask to try the camera then shoot some video with your memory card in.
Then you can bring your memory card home and try it out.

I've done this with a digital SLR so I could check out the image quality on my computer.