I was really oversold on the "maintenance" and "reliability" concerns of index versus friction shifting, but I don't tour out in the middle of nowhere so it's really not a concern for me. And, so far, my limited index experience has been great.

In general, I believe the Shimano "road" long cage derailleurs shift 28t (maybe 30t if dialed in just right), Campagnolo long cage shift 29t and Shimano MTB derailleurs up to 34-36t.

I've found that if I'm not hauling much weight a 1:1 gear on 700c is plenty low. I think 9 is a sweet spot with lots of options including Shimergo.