My Sun(female) conjunct his Vesta/Pallas/Pholus. I would like to find out does this means and what effect it has on a relationship if any. Also my Sun trines his North Node is that positive in synastry?
Vesta is, amongst others, about purity and sexuality. Sun conjunct vesta in synastry suggests you are the right person for him to open up at that level. He may treat you as something sacred in his life. You are likely to bring him mental clarity too.
Pallas is a pattern weaver. So, Sun conjunct Pallas suggests you have the right personality for him to like you more and more as he gets to know you. You will appreciate his efforts to make the relationship work.
Pholus is about facing the consequence of other's addictions (amongst others). So sun conjunct pallas suggests you have the right personality to help him with those issues, for example an abusive parent. But it is also about extreme activities such as extreme sports. If you are into it, this aspect helps.
You sun conjunct his north node suggests you have the kind of personality that will support him developing his under-developed qualities required to solve his personal 'karmic' life challenges.
All in all, it seems you are the perfect partner to let him fix his stuff (if needed) and to develop a profound and lasting relationship. It is very positive. Unless there are many other unsupportive aspects, time is on you side.