This cardigan can be worn oversized and slouchy. If you make a larger size you could even belt it in a kimono wrap style. It is a wide, flared fit so a smaller size than normal may be more suitable if you want a less casual style.
The pockets are optional - see our second colourway image for how it looks without pockets too.
Even though circular needles are specified you are still working back and forth in rows, not in the round. The circular needles are simply used to accommodate the number of stitches cast on.