I have taken and re-taken Joel's course as his thinking has evolved. He has some good stuff there, and I will probably take it again someday to see how his thinking continues to evolve, and how my own progress evolves as I become more aware of things that I may have missed the first time around. I have also taken Jim Casto's course, and highly recommend it to anyone. Taking both together is great; they compliment each other, like approaching a common problem from two different directions.
Underlying both courses is the concept that you will conquer your target panic when you are able to put your mind into a psychological framework where target panic does not exist. For me, for example, target panic does not exist when I am drawing the bow without the intention of shooting it. If I could simply “think” my way into that frame of mind, I would do it, but most of us need some help to move from an undesirable frame of mind to one we we would prefer to be in.
Jim's method helped me to accomplish this with baby steps. The first step was to start drawing and shooting the bow under conditions that were as close to drawing and not shooting the bow as it is possible to get. This allowed me to stay in the same positive frame of mind when drawing and shooting the bow that I had when drawing and not shooting the bow. This was reinforced by adding a tiny bit more realism to the shooting process every day, until I finally arrived at the place where I could draw and shoot the bow freely under more stressful conditions and yet retain the same psychological frame of mind I have when I draw the bow without the intention of shooting it. This connection is fragile at first, and can be easily broken if one doesn't follow Jim's plan from beginning to end without deviation.
Joel does that by using a non-anticipatory psychotrigger. The trigger itself is not as important as knowing that until the trigger is engaged, the shot process is no different from drawing the bow without the intention of shooting it. The decision to shoot is not made until the trigger is actually engaged, and can and should be stopped even during the movement to activate the trigger if something goes wrong with the shot process. This makes it fairly easy to adopt the same frame of mind you would have if you were drawing the bow without intending to shoot it, as long as you take the decision to shoot or not shoot seriously and really do let down from time to time. After making the decision to shoot, you must learn to concentrate on the activation movement to the exclusion of everything else, to the point that there is no room left in your narrow cone of concentration for target panic to intrude. While by no means easy, most people can learn to effectively focus their concentration on the activation movement for the 1 or 2 seconds it takes to complete it.
Most people that use a trigger use a clicker or feather to nose system. The advantage of these methods is that they include a draw check in addition to the trigger. Also, they involve no unnecessary movement on the part of the shooter. The disadvantage is that a clicker involves extra clunky gear, and feather to nose is a movement that some people don't like to do. Neither of these works very well for shooters who use a dead release, which I believe is why Joel developed sear triggers.
As far as whether you should use a grip sear or a tab sear, both involve unnecessary movements that could potentially interfere with the shot. So try both and use the one that you can execute with the least interference with your shot. Probably this varies from person to person, which is why some use one and some use the other.
Keep in mind that as your control over target panic grows, there will come a day when you no longer need to use an external trigger. Most of the best trad shooters in the world don't use external triggers. AFAIK, all the top shooters in the Olympics use clickers whether they have target panic or not, because of the draw check. Don't rush it, but keep it in mind. You'll know when you're ready.