Traveling light makes the trip more pleasant in many ways, but even when traveling light I don't think minor differences in the bike have a huge impact either way on the touring experience. Better components and carbon forks will make very little difference in the overall experience. Still if you make 5 pounds of difference in bike weight it will be pretty noticeable especially when climbing, so yeah a more road bike type bike may work well if going very light gear wise.

Be sure you have wheels that will stand up to the demands, a comfortable for you riding position, and low enough gearing and all else about the bike becomes not such a big deal. In the end the bike is a minor factor as long as it is reasonably suited to the task at hand. Throwing more money at it won't enhance the experience much.

I suggest that you figure out what works for you when it comes down to riding position rather than just following either a roadie approach or a "standard" touring approach. I find a road bike like position to be most comfortable for the long mileage days. Others insist on bars at or above the saddle. Figure out what works for you.

What ever you do with regard to bags, I would say to avoid using a backpack. On our TA we had many consecutive 100+ F days and anywhere clothing rubbed us a little we got heat rash. I can't imagine how miserable a backpack would have been.

A few things to keep in mind are that you will need to carry enough water for at least 80 miles in possibly 100+ heat and that there will be some fairly long sections of very rough pavement due to road construction. If you could be sure of good roads and are traveling as light as you plan, I would say use skinny tires if you want, but given the roads we had at times I would advise at least 25-28mm tires if going ultra light gear wise.

Oh and be sure to enjoy the people and places. A fast pace and long miles are OK, just don't forget to enjoy the trip too.

Edit:
You mention 3 days of food... No need to carry more than the days food and an extra emergency meal or so. Most of the time you can buy food as you need it. Either stop at the store before making camp or ride there after. On the TA it makes sense to stay in town most of the time. The TA maps will list city parks, churches, etc. and staying in them works out well for the majority of the trip. There were some places in the west where we stayed in unmanned forest service camps that were kind of remote, but not often at all.