Nice tank! I have three of those cubes, but could never get the hardscape looking "right." Yours looks great.
I have a Betta in a 1.5 and he has eaten 4 ghost shrimp in his lifetime, but those shrimp are only .36 cents a piece. You might have better and more hiding places for your shrimp. I found that as long as I religiously feed my Betta he usually leaves the shrimp alone
I have one betta that lives in a 2.5 with shrimp and never bothers them. Another that hunts down anything that moves. It even took awhile for him to leave snails alone. He kept nipping off their antennae (or whatever they're called on snails). I'd recommend OP start with just a couple of cheap cherries and see how they do.