Tire size, you really need to make sure the tire will fit between the stays, under the fork crown, under the rear seat stay bridge, Djb (above) is guessing 37, but if you previously ran 27 X 1 1/4, you might be limited to 32mm. And that impacts your rim width. Since the bike previously used 27 inch, then the width between the fork blades and between the chainstays is likely the limiting factor, as the space under teh fork crown or seatstay bridge should be quite good. That said, on my folding bike the width between the chainstays is the limiting factor.

I think the chart at the bottom of this page is very good for sizing rim inner width to tire width.
https://sheldonbrown.com/tire-sizing.html

Also, consider that many of us that do touring like to have fenders for those wet days. My light touring bike frame is adequate for up to 45mm tires or 45mm fenders with up to 37mm tires. Point being that you should decide soon if fenders are in your future, as that impacts max tire width, which is a factor in rim decision.

I am guessing you will conclude that inner width of 17 to 19 might be about right if you use a 32 or 37mm tire width. I run 37mm width on my light touring bike (with the Dyad rims I mentioned before), that works pretty good on rail trail or towpath type gravel trails, but on occasion I wish I had a bit more width. Maybe you got lucky and Rodriguez made enough room for wider tires?