不见得means you have your own opinion,which may be different with the commonsense or other peoples' perspective. For example,虽然他很弱小，但不见得会输。 不一定means there is a possibility to lead to another outcome.For example,今天不一定会下雨。 依我看=to my opinion.依我看，我们还是走吧。 要我说=when it comes to me.要我说，你是对的。The two statement are almost the same.

不见得跟不一定意思相近，但是 不见得 多用于表示反对意见，不一定是中性的，可以随意用，依我看跟按我说，是一样的用法，没什么区别

The first one You're not sure. Uncertain. In my view. In my talking

哪来的这么多幺蛾子……（开玩笑）