Touring bicycle must-have features
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.