I have a Chambers Fowler I am just starting. I just finished my first one, but it was a Traditions Kentucky kit and they are not as in depth as kits from the vendors you mentioned. I used it as project to learn basics. I added an inletted piece and some small embellishments. Check out Duelist1954 on Youtube. He has a series where he builds a Bucks Co kit from Track of the Wolf. It will give you an idea of what you are in for. I've been planning my Chambers gun for a while and have to say, I've bought a lot of tools!
I guess it comes down to what you like to do. I enjoy the build part just as much as shooting. If you want to get right in to it, a built rifle is the way to go. I have a Pedersoli KY rifle but haven't shot it yet. I've heard nothing but good things about them.
An "in-between" alternative is to get a rifle "In the White" (TVM sells them that way). All you have to do with those is the stock and barrel finishes.
Here is part 1: