Get swept back bars like on Pashleys and Linus bikes.
70 degree and about 60 mm rise is best IMO, with which I have done both my tours totaling 8,100 miles. They are old chrome ones, 48 and 52 cm c/c.
My TT is 610 mm with 76 mm stem. Back positions are more important IMO. I often have my right hand on the bend, no padding required. My 1973 grips are both smooth plastic, comfortable in any temps or weather. My other old bike has a 23.5" TT. I am 5'8".
Straight bars are torture devices.