Ideally, you want a little free-play in the throttle. If the throttle has no play, it is possible the throttle will move when the bars are turned, mostly if the cable is not routed correctly.
Now, can the idle be adjusted with the cable or the carb cap crews without experiencing any problems? Yes, I just think it should be adjusted the correct way. Idle screws for the idle, cap screws for the slides, and cable adjuster for throttle free-play.
Stock carbs are cheap, and I would bet many people have a set lying around collecting dust (I know I do). If you are not wanting to install idle screws in your carbs, you can probably get a set of stockers already modified pretty cheap.
Installing an idle screw kit is very easy and inexpensive, so to me, it is worth the time and money to do it right.