Sure, you can do a deca-only cycle. I'm doing just that right now and certainly enjoying it. It really depends on how you react to gear. I can't stress this enough to first-timers. I never get deca-dick so that simply isn't an issue for me. In fact, I probably sport more wood on a deca-only cycle than I do when I'm off cycle. Also, for me, deca is NOT easy on my hair...I lose just as much hair with deca than I do with any other androgen, so that may or may not be an issue with you.
You won't experience a tremendous amount of bloat like you can using testosterone. Interestingly, though, I've had more blood pressure problems with deca than I do with test, probably due to significantly elevated hematocrit & hemoglobin levels. But you will make very solid progress and gains if your diet, training, and recovery are all in order.
If you react very favorably to gear like I do, 200mg/wk will be plenty...I'm actually going to knock down my 400mg/wk to 300mg/wk and try to lower my blood pressure a bit. If your body isn't as receptive to gear, then you may not be thrilled with your results. But my position has always been it's better to be safe than sorry. You can always run another cycle with a different dosing schedule.