If you make mittens, chances are you will need to use 2 circs or magic loop. To do small diameter knitting in the round, you either need dpns, or the 2 circs or magic loop method. Unless you find a circular needle with a very short cable.
The thing with circular needles, you need enough stitches that will go around your needle. So if you have a 16in cable, you'll need to cast on quite a few!
This being said, apart from that, knitting with circular needles is the same as on DPNs. In general yes you do put a stitch marker to make sure you know where the beginning of the round is. And if it makes your life easier to mark the places where, in principle, your stitches would be on a different dpn, go ahead, why not!