With a touring bike, you want comfort as your top priority. That comfort means you have to get something the right size, with a good way of carrying your luggage out of yor way (heelstrike) without being so far abaft that it affects the line. Comfort means getting a position - or positions - which you can maintain all day. I used to favour a randonneur bar, but there isn't a decent one on the market any more. I tend to ride almost exclusively on the hoods these days, so I'm considering switching to bullhorns like my commuter. Everyone is different. I like a lower, more stretched, posture. It works for me, but a lot of people prefer something more upright.
Comfort covers being able to shift a load up a hill in the most effective way. So choosing gears is important. I know that I like a range of 25-100". Anything lower gets wobbly for me, though I know people who climb quite steadily at a glacial pace.
Although you want a strong and reasonably stiff frame to carry your luggage, it needs to be pliant enough for comfort. I have a penchant for steel, and Reynolds 531 in particular. There's a good choice of materials these days, and I'd say a number of different alloys will give you similar characteristics, depending on nuance. Steel is easier to repair if you come to grief far from home as it can be welded (mostly), and brazing is a fairly common skill worldwide.
The bottom line is to test things out. There's not much point in getting a custom build as a relatively new tourer, as you won't know just what suits you. As a starting point, it's hard to go wrong with a Ridgeback or something like a Dawes Galaxy.
Good luck in your search, and hope you enjoy whatever you end up riding.
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