What are the good exercises to shape vowels and not tense up, but project sound? Thank you!

A well formed vowel in the right part of the range should create an efficient resonating shape that releases tension. In women's voices, I like to start with the [i] "ee" vowel in the middle voice. Make sure you are forming this with your tongue and inhaling to feel a cold spot on the roof of your mouth. Then send the sound there while you are singing on the [i] vowel. For more clarity on vowel shapes, check out Derrick Goff's Intro to IPA. He does a great job explaining this in detail :)