Terri~always happy to enable! Personally, I can't seem to get enough of heucheras/ellas! I like that they'll grow just about anywhere, unlike other plants that need mostly sun or mostly shade.
I've had lots of luck with heucheras in full sun. Out of the three you listed, I grow Miracle and Peach Crisp. They both grow well in full sun and Peach Crisp acutally needs some sun in order to color up. I don't like Miracle very much. It's green most of the year and doesn't color up nearly so nicely as the pictures show. One I do have that has those particular colors is heucherella Solar Eclipse. That one grows in full sun and is a much better option, imho.
I grow most of mine in lots of sun, except for the lime green and yellow ones. Those seem to need at least afternoon shade, if not all day shade, or else their leaves burn to a crisp.
As a general rule, the darker the leaf, the more sun the plant can take. I grow Palace Purple, Blackout, Frost, Blackberry Crisp and Midnight Ruffles in hot afternoon sun and they don't scorch unless I forget to water them. The only thing I notice with the full sun is that they tend to "green up" a bit in the heat of the summer. They go back to being purple in the spring and fall, though.
Others I have luck with in full sun are Caramel, Amber Waves, Melting Fire, Sashay, Rio, Mahogany, Big Top Gold, Zipper, Venus, Geisha's Fan, Marvelous Marble, Brass Lantern and Green Spice. All of my others I have in afternoon shade, so I can't attest to their sun tolerance. I suspect they'll take more sun than I'm giving them, though.
I should also note that I've noticed that adequate watering plays a big part in how sun tolerant my plants are. If I forget to water, even the ones that are listed as "full sun" plants will get crispy leaves.
I grow over 70 varieties of heucheras and heucherellas. If there are any others you're looking for specific info on, let me know and I'll see if I can help.
Q