I don't have creme fraiche, but I do have cream. Could I use all cream in this scone recipe? Is the sourness and thickness of the creme fraiche im...

If I had cream but no creme fraiche, I would absolutely substitute. If you add a bit of lemon juice and let it sit for a few minutes, it will thicken up and taste a little tangy. In any case, since you're making a substituion, you'll want to gauge the quantity of cream you use based on how the scone dough comes together, not just based on the measured quantity.

1/4 buttermilk with greek yogurt should work with a similar effect.