I have experimented switching between the two styles. I shoot the Scott S2 wrist release and a Carter Too Simple Thumb. You will likely experience some point of impact shift, depending on your anchor between the two, as most people anchor lower on the jaw with the thumb which makes the peep heights different. It may not be easy going back and forth. I had to change my wrist release anchor to get my peep to line up.
I haven't been able to adjust to the thumb barrel though as well as I would like. I compared the two by shooting at a pie plate with a 3in circle drawn in the middle at 50 yards, one plate for each release. It was easy to compare the accuracy of both releases that way. I wasn't really looking to see how each hit the inner circle as I figured the thumb might shift my impact. I was comparing group sizes really and It was clear I am a better shooter with the wrist release with tighter groups. Now that could be because its what I've shot the most for years, and feels more natural, so maybe I just need more time with the thumb release? Not sure.
FWIW I've also shot a Stan Perfex LN and SN, Stan Onnex Thumb/Hinge, Carter Wise Choice...tinkering with all of them.... I prefer the Carter too simple, as It has a shorter neck so it maximized draw length.
I'm really leaning towards just selling the thumb and giving up on the idea completely. I shoot the wrist better, but I hate the fact it dangles from my wrist all the time, clangs on things...gets sweaty...