FWIW,If you're thinking of either a Surly Cross Check or Straggler,the CC is the better option of the two IMO as the Strag's rear disc brake mount is in the wrong place for a touring bike and leads to bodged up rear rack fitting or the rack fitted more rearward than needs be(as per photo above)than if the D/B mount was fitted to the chainstay,where is should be.
You needn't worry about the CC's horizontal dropouts they are just as user friendly as the Strag's and wheel fitting is just as easy with the stop screws provided with the frame(same as the Strag's).
TBH I wouldn't touch belt drive for touring with an extremely long barge pole.It limits the rear hub to IGH which limits the hub to Rohloff for reliability(forget Shimano Alfine 11,they aren't reliable enough there's a thread on here somewhere proving my point).If you're thinking of a Rohloff,ride one first they don't suit everyone.
Meic's point about getting the bars high enough could be a valid one but a problem that can be overcome with a extender should you need one.
TBH for you commute if it's flat enough for SS/fixed gear I'd buy a cheap secondhand bike for that duty,and buy a decent tourer for day rides and touring.You then don't need to worry about changing things over,adding gear levers,mechs,etc,it's by far the simplest option and you won't fret about leaving it chained up on the street.
Should you do that you're then left with a choice of:- Surly DT,LHT or CC,Salsa Vaya,Spec AWOL,Cinelli,all dedicated touring bikes but with the AWOL and Cinelli being unknown factors,and the Surly DT & LHT having a sound reputation for being round the world tough as old boots expedition tourers,with the Vaya and surly CC also having a very good reputation though not as heavy duty as the Surly LHT/DT,though the Vaya only goes up to 60cm but TBH I think that's big enough.
Ultimately the choice is yours and by process of elimination you'll arrive at the right bike
