Bowling Action varies one individual to other, some prefer bowling side on and some prefer bowling front on. Each action has it's own advantage and disadvantage. Alignment of the backfoot landing, front hip and the front shoulder will usually detemine the bowling action type.
Most of the bowlers in the modern day cricket have side-on Action and the coaches also incourage the bowler to bowl with side on action. Side on action hepls the bowler to swing the ball away from the righ hand batsmen.
Front-on action is opposite to side-on action. Front-on action helps the bowler to swing the ball in to the right hand batsmen.
Mixed action is usually the combination of both the side-on and the front-on action. Mixed action should be properly looked or else the bowler may end up getting injured.
Hips and the shoulder should be always in the same line and if it is not in a same line then it means that the bowler is twisting his back which can result in the serious back injury.