How you throw your jab is utterly dependent on what you are trying to achieve with it. As others have mentioned above, if you are trying to maintain distance then I find that flicking the jab out on the move, be it backwards, or laterally is the best way to go; however, there is also a case for getting someones respect with a stiff jab, you can achieve this by flicking the jab out on the move and then step in with a firm jab - this will keep your opponent guessing. If you are fighting a pressure fighter, utilise the same flicking jab, whilst moving laterally to keep him/her turning - sometimes I like to pivot whilst throwing the flicking jab, and throw in a straight left (southpaw) as my opponent turns into it. Then you have the option of stepping into your jab, you can utilise this if you are shorter than your opponent, or if you spot a weakness in your opponents defense that leaves them open for a stiff jab. I also like to step into a jab when i'm going to the body, I feint to the head and jab to the body. There are tons of options when throwing the jab, don't limit yourself to one style. If i've said this once, I have have said it a million times - the more options you have, the more problems your opponent will have!
Thanks for all your help. I guess a mix is best for different aspects of the fight. Its just gonna be hard breaking the habit after 3 years haha.