421 into Boon NC isn't a bad choice just it's a little longer travel then to use 321. The drive up into the mountains on ether is four lane road. I have a home in the Boone area and drive both frequently. The road graded on both 421 and 321 are about the same and you're going to be giving the tow vehicle a little bit of a work out but it not drastic. The scenery on both roads is good but I like 421 a little more then 321. If you use 421 watch your speed going through Wilkesboro NC. and if you use 321 do the same going through Blowing Rock NC. Both towns have some LEO that love to sit at the bottom of the down hill grades and pull you over to have talk if your speed is more then the limit.