All your questions really come down to personal preference (i.e., no right or wrong answer), especially if your plans are to tour only in North America and Europe.
My personal preferences:
* 26” (ISO 559mm) wheels are considered universal, so it's easy to source replacement tires, rims and spokes anywhere in the world. But you won't encounter difficulties sourcing these in North America or Europe with 700c. I agree that 26" wheels start looking funny on frames larger than 58 cm, although they still look OK once you install fenders which I highly recommend anyway.
* Handlebars: After having used both, I would favor MTB flat bars with bar ends such as Ergon's GS3. One word of caution: you need to be careful on choosing your LHT frame size with butterfly/flat bars or you risk your fitting being totally off. The LHT's geometry is optimized for drop bars. There are other bikes in the Surly line-up that will work better with flat/butterfly/Jones bars.
* Mechanical disc brakes hands down over V-brakes for me.
Last edited by Chris Pringle; 11-19-15 at 09:45 PM.