First off, stop thinking of the 3-2-1 method. Just get it right out of your head. (disclaimer, the 3-2-1 method is a perfectly fine starting point, but I think it leads folks to believe it's the only way)
Start thinking in terms of what happens to your ribs during all of the cooking phases.
#1: The smoking phase. This is where the ribs get their smoke flavor and that beautiful color. They will also
partially cook and tenderize here.
#2: The Braising phase. This is where the connective tissue in the meat does most of its breaking down and the ribs get really tender.
THIS IS VERY EASY TO OVERDO!!
#3: The Setup and/or sauce phase. This is where the ribs have a chance to firm up and the sauce has a chance to set. If you haven't overdone #2, this phase is really only about setting your glaze or sauce, since the meat won't need to firm back up because it hasn't been cooked to the point of falling apart.
Now, I'm not a competitor, but I do love my ribs to have a firmer texture. Fall off the bone is WAAAY overdone for me. My method is pretty simple. I crank my heat to 275˚ and let the ribs smoke until the color and crust is about where I like it. Timing wise, anywhere form 2-3 hours, though I usually don't keep track. Next, for the braising phase, I'll wrap in foil with some acidic liquid. Yes, I add other flavors, but we're talking about texture here, so the really only important thing is having some sort of acidic liquid. This will help break down the connective tissue. I leave them in the foil for 45 minutes then I'll check. If they're not quite there, I'll let them go another 15 minutes. When they hit the tenderness I like (roughly the consistency of perfectly cooked pork tenderloin or a ribeye steak) I'll pull them out of the foil and glaze or sauce if I'm using it. Then onto the grate again for 10-15 minutes just to either set the sauce or let the surface moisture from the braising phase set up so they're not wet and slimy.
And that's pretty much it.
The 2 racks in the pictures were both a while ago, but both were right exactly the perfect texture for me. I certainly don't nail it every time, but it's fun trying!