Pay attention to aerodynamics. Like weight, it's energy saved, faster travel and easier on the body. Try to resemble a teardrop - wear a tight shirt, arm sleeves and leggings instead of flappy clothes, use a frame bag or saddle bag or rack bag, not panniers, and train yourself to ride in a more aero position. Look into aero bars - I don't use these any more as I do a "faux aero bars" tuck on drop bars.
Drop bars are my favourite, gives great control in the drops when descending and lots of hand positions. Consider a moustache bar if the tour is slower. Riding on the hoods (slightly tilted inwards) is the most aero position after the preying mantis TT tuck.
get a narrow bar. You can go really narrow and still have control, even at 28mm. Biggest aero benefit.
alternate your leg muscle use. "Lift and drop" your legs when they get tired from pushing, aka swap from quads to hammies to adductors. Only aero tuck on the flats to save your back muscles, relax when going downhill.
Forget a suspension fork on all but the nastiest routes. Ride like a mongolian horseback archer on rough terrain, and keep your feet at parallel levels when descending bumpy roads.
You can do really bad terrain on slick skinny tyres. I ride 28mm-32mm and wouldn't want anything else even if the route was 50% off road. Tread is a meme for most scenarios beyond thick mud and WILL slow you down on the road, despite marketing. Choose a tough rear tyre and a fast front, nearly all punctures happen on the rear as it gets most of the weight.
Use gel gloves with ulnar pads or bar inserts if you feel nerve pinching coming on in your hands, these will also reduce fatigue.
Nothing wrong with a disc rear and a deep (50mm-70mm) front if you're a heavier or strong rider. On crazy high wind days I just take a break, wouldn't want to ride on any bike on those days.
If you're doing long dull road stretches learn to skitch and draft trucks. Good channel:
https://www.youtube.com/watch?v=vO54JAeIOHQ 
