Yes, shooting split vs 3 under can change the way the limbs load when drawn. The particular bow you're shooting my perfer one string grip over the other. I've had a few bows that didn't like a 3 under hold at all and where hard to tune for shooting that way.
The change in string grip is going to feel strange for bit, as will your release, until you adjust to the difference in pressure on the fingers. Being you are, as you said, a "newbie", take some time and experiment with shooting split. You may find it suits the style of shooting you want to pursue better than 3 under or, after a bit, you may find it doesn't. If it doesn't, move on and find something that does. Eventually, you'll develope a shooting style that fits what you want to achieve.