I'm new here and your post caught my attention because I use them in combo smoking with woods.
My personal preference is a "smoke pouch" consisting of equal parts basmati rice and brown sugar, shallots and an herb mixture I get (shallots, onion, garlic, thyme, rosemary, basil, coriander, lemon peel, black pepper, chives, green peppercorns, dill weed and orange).
I've used this on about everything for bbq smoking mainly pork and pork ribs, chicken, turkey and beef. Typically, I use about 3/4 cup each the rice and sugar and about 3/4 tablespoon of herbs sometimes more or less depending on quantity of meat. I will add an additional shallot clove to the smoking pouch as some directly on the fire. I have even put a couple two or three inch pieces of corn cob in there from time to time for pork. And (cloves) too but just a touch for a hint of flavor.
This method originated in Asian smoking using dry teas instead of herbs. When I first experimented with this I found that the pouch directly on the grate above the fire was too hot. So, I now put it atop a small smoke box that's sitting on the grill grate to prevent it from getting to terribly heated. You can also adjust your coals in this way so the pouch is stituated where it's getting adequate heat without scorching.
*If you're cooking/smoking for longer periods of time, make sure to remove the herb pack prior to the mix becomming very charred. A little bit around the edges is ok but if it all of that "stuff" gets to the point where there's not much moisture left getting burnt you're going to get a burned, scorched taste. If you're grilling for shorter periods this will be less an issue for me an hour or so is about max. Plus I want to avoid that type of smoke in my cooker.
If it's something you like to match up with a particular meat I'd say that it is probably alright whatever it is to make a smoke pouch or the add herbs directly to the coals for smoke. If you just want to add the herbs to the coals you may want to consider combining them with a little bit of water making a paste. I think you'll get a little more flavor that way their smoldering rather than quickly burning.
I've learned that less is usually better to begin with and then scaling it up if necessary.