Your grandpa had it right; smoked carp are delicious. Seventy years ago, when I helped two uncles who were commercial fishermen on the Mississippi River, we sent tons of carp to markets in Chicago and New York for "gefilte fish," and we smoked tons more for local Illinois and Iowa markets as well as for Chicago. We got the highest price for smoked sturgeon -- the best smoked fish there is, besides having no bones -- and so we kids did not get all the smoked sturgeon we wanted, but we got all the smoked carp we could eat.
This nonsense about "muddy taste" is coming from mouths that have never even tasted smoked carp. The Upper Iowa River, where I sport fish now, is NOT muddy (trout water and smallmouth bass), and so carp from it would have no excuse to taste "muddy;" the Mississippi River can be muddy, but I see no difference in the flavor of smoked carp in our local supermarkets from the Mississippi.
My uncles used only apple wood to smoke fish; but, not everybody does, and I have used many different kinds of wood with good results (if somewhat short of the ideal of apple wood). I even got a very good/special flavor using lilac wood to smoke various meats and fish.
As far as I am concerned, the bigger the carp, the better, making the bones, therefore, no problem at all. Most of the carp I smoke are in the 10-15-pound range, but my uncles often did carp and buffalo in the 30-40-pound range. When times were extremely busy, they did not even brine the fish. I usually salt brine in the refrigerator overnight. I do not bother to scale the fish (smoke them scales down), and I steak them into 7-8-inch steaks split along the backbone. Anyone who wouldn't like my smoked carp, buffalo, and sucker, wouldn't like smoked fish of any kind.
P.S. I share the view of the people who love to eat catfish. As a teenager, I saw a fisherman at a lake in Massachusetts, throwing catfish onto the bank and leaving them to rot. I asked if he didn't want those catfish, and he said, "Around here, we call them 'hornpout' and nobody eats them." I said, "Well, I'm from Iowa, and there we call them catfish, and they are delicious!" Maybe if I had mentioned how got they are fried in beer batter, he might have reconsidered his untested bias.