Big questions
What I've learned from preparing for a trip:
Being in good shape is helpful, but more importantly having a comfortable bike will far out last the time you spend on the bike.
Geometry and not only have a good saddle, but being ready to stay on that saddle for hours.
If you have set destinations, it's best to take a few rides with a loaded bike to see if those distances are good for you. Too short and you might get bored. Too far and you will wear yourself out and probably never bike tour again. Knowing your limitations will make the trip more enjoyable. Set aside entire days for prep riding to see what your limits are.
Also, the more time you spend riding, the better shape you will be. So your first day, compared to a week later could make the difference in 20-30 kms a day.
Set a route, but be ready for anything. The more confident you are in your ability to change plans and adapt, the less nervous you will be in doing it. Eg: Getting lost (or a little confused) is not a problem, it's an opportunity
Finally: Enjoy yourself. If you want to admire a view, do it. If you want to stop for a coffee/tea, do it. If you want to take a nap on the grass, do it. It's not a race, it's a vacation.
