一般过去将来时
形式:would+动词原形和was/were going to+动词原形
用于描述过去某时间里你对于未来的想法和猜测。

虚拟语气(此处我们谈论对现在和将来情况的虚拟)
形式:would/should/might/could+动词原形
用于描述不能实现或者纯粹是家乡的情况。

例句对比:
(1)
I was sure that I would work in a small city when I was a child. 在我很小的时候我就觉得我会在一个小城市工作。
If I were you, I would choose to work in a small city. 如果我是你,我会选择在小城市工作。(事实上我不是你)

(2)
You told me that you would talk with your parents. 你告诉我你会和父母谈谈的。
If you talked with your parents, something wouldn't happen. 如果你和父母谈过了,有些事就不会发生了。(你没和父母谈过)

(3)
She hoped that when Nixon told it to me the next morning I would not give him a hard time. 她希望第二天上午尼克松同我谈起这件事时,我不要使他难堪。
If she told me about this, I wouldn't give Nixon a hard time. 如果她告诉我这些,我就不会让尼克松难堪了。(她没告诉我这些事)

是不是感觉二者很相似?其实虚拟句和过去将来时最大的不同便是虚拟句是纯粹的假想,不会发生的事情。而过去将来时则是计划会发生的事。