Bow Bender the answer is yes to all of your questions.
I shot with a competition shooter in the 70s that used one because he had arthritis. His name was Howard Schofner (in case any of the older Jersey guys here remember him). He competed in classes that were bare bow fingers (don't know what they called the class). He started to clean up because he was such a good shot. They changed the rules and deemed it a release back then (I think to force him out of the class). I imagine in competition it would still be considered a release today. Back then we shot both compounds and trad instinctive with it. Another friend of mine would shoot a 70# longbow with one and also shot it like a rifle (if you ever try one you will know what feat that is).
The strap gets wrapped around the string from your index finger towards your thumb and your bow shelf is the same as though you were shooting fingers, since the direction of tension is the same as fingers.
Years ago I was shooting with Bob Wesley. He shot two under split finger and so did I at the time. He said to me, "Gil it is hard for a split finger shooter to beat a 3 under shooter". I never forgot that and tried to master 3 under, but just couldn't get it, so I went back to my wrist tab. Since I lost mine I made a simple one that just went around my fingers. It is the light brown one in the picture in my other thread. It works great but is uncomfortable compared to the original wrist tab.
The wrist\thumb tab is extremely smooth. It expands your draw (with fingers I am 28.5" with the wrist tab I am 31"). It enables you to raise your anchor up close to your eye (like a 3 under shooter) and the fletch to touch the inside of your nose adding another anchor point. Since you raise your anchor it decreases the gap between your arrow and eye, thereby reducing the margin of error. By increasing your draw it forces you to hold with your back muscles and puts your drawing arm elbow in Terry's 6 o'clock position in his shooting clock. It also lowers your drawing elbow. You will also notice that upon release your drawing hand goes back and there is no creep since you have expanded your draw, touch your feather to your nose and lock in your anchor with your back muscles between your shoulder blades.
At first start to use one on a lite bow until you get used to it. It first feels like it wants go until you get used to it (and you might actually let a few fly while drawing). The secret to using one is to make sure that when you grasp the the string with the tab the folded tab is behind the first knuckle of your thumb and deep into the web. If you do this you won't let any go on the draw. If you shoot a very heavy bow it will take you a long time to master only because of the weight. You will have to strengthen muscles you probably have never used. I never had the strength to be able to draw over 60#s with it.
I am just back to shooting after a two year lay off because of a fourth bow arm shoulder injury. I am shooting a lite 45# bow and shooting pretty good for having a long layoff. I was shocked to be honest. I attribute that to the thumb tab. I think if I were still shooting split finger it would have taken a lot more time to get back. I still have a lot do to get completely, back but it is just great getting back to trad archery. It has been a big part of my life for 60 years.
Look on Youtube for Talon Thumb Tab. He is a sponsor here, but I am not sure if he still makes them. You will see how he uses his. It is a good place to start to understand how they work. You may want to just make one like my finger tab in my thread. You just need a strip of 1/2" wide leather (3mm 5-6 oz) and a small dowel.
I will watch this thread in case you have any other questions.
Gil