What should I take in consideration as an important feature(s) for a touring bicycle?
My goal is to use it for long distance trips and eventually work commuting.
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I'd go for a longer bike rather than a short one. This helps handling at speed and makes it easier to hold a line. A shorter bike needs steering input all the time, whereas a longer / more relaxed geometry will track by itself, but will need more effort to turn.
A packbike is no use if you can't carry the things you need. For some that might be as little as a water bottle and a credit card. Other riders might want to pack along a kitchen sink and every possible convenience. How you fit it all on the bike is a separate question, but rackmounting lugs in the frame will be easier than trying to fudge things.
You should look at handlebar positions too - long distance riders like to have many hand positions, so at least have barends on a flat bar, or have drops, or have trekking/butterfly bars.
Saddle comfort is important too - whatever works for you.
Mudguards/fenders, because not every day is good weather.
Lights, both DRLs for safety in the day and full-on lights for night riding. At least two front and two rear. If you can go one from a dynamo that will give battery-free riding.
Reflectors - they only work when a light is shining at you, but they're small and light and completely autonomous. I use DOT tape and stick portions to parts of frame. I also have clip-on wheel spoke reflectors to replace the yellow plastic block ones. They're excellent.
Consider that your work commuter might be a different bike - the risk there is theft. So a nice touring bike will vanish pretty quick if locked up outside.
Long wheelbase and relaxed geometry for stability. Low bottom bracket. Long chain stays, otherwise you'll catch panniers with your heels.
Mounting points for full mudguards, mounting points for rear rack and front rack (if you plan to carry a lot). Plenty of bottle cage mounts. At least 2.
Wide gear range, and a low bottom gear. My tourer has 22 gear inches at the bottom. I've got up every hill so far, but I would like even lower than that. It depends where you're going of course. A 3 x 9 setup can give you a very wide range. Mine goes from 22 inches to 118 inches.
Probably drop bars or something that allows multiple hand positions. My tourer was the first time I'd used drop bars. At first it felt strange, but now I really appreciate the ability to change hand positions - the flats on my hybrid give me wrist pain very quickly.
It's hard to give good advice without knowing more about the kind of touring you plan on doing, but assuming you plan on a conventional self-supported setup, one critical feature to look for is chainstay length--too short, and you'll be striking your rear panniers with your heels with every pedal stroke.
Another important feature is predictable steering. Some bikes are designed for maneuverability. You want one that emphasizes stability. And if you're going to be carrying a load on the front forks, you want a bike where the steering has been designed to accommodate that.
Also important (but easy to change) factor is gearing: you need gearing that's low enough to get you up the steepest grade you expect to encounter, loaded with however much gear you'll be carrying, after however many miles you might have ridden that day.
You can always fix stuff like tires, saddles, etc, but you can't fix a frame that doesn't suit your purposes. Happily, there are plenty of dedicated touring bikes out there that have already sorted all this stuff out.