Originally Posted by
cyber.snow
... I am finding 1 3/8" (35mm?) 1.5" (38mm?) and 1.75" (44mm) ...
Make sure you get the correct 26 inch tires, you want 559mm bead diameter.
Tire size 1 3/8 is different, that was common on british three speeds decades ago and will not fit. You did not mention 1 1/2, but that is also out there, later that obtained the name 650b and in the past year or two some manufacturers have started calling that 27.5.
26 Inch Bicycle Tires
For mostly road riding you are looking for 1.5 width. Narrower tires are possible to find, but rare.