It's tricky. You're probably safer going by trichs.
You pretty much have heard cloudy=heady amber=body
What does 50% red pistils say about the high? Nothing.
Pistils are too general. Trichs are a bit more precise. Although not much is set in stone.
And you don't need a microscope. Once they start to amber up, you can see with the naked eye.
Checking one or 2 small leaf tips doesn't give you that good an indication. 5-15x loop is all you really need.
I only use this to make sure i don't have many clear trichs.
But you really can see the color change from cloudy to amber without an aid. At least the strains i grow, i can.