Interesting questions, which I have not analyzed mathematicly. But in most GOTMs, we can IRB in rows 1 and 2 very early in the game without effort. Often, we start with either BW or HBR. If not, I usually choose BW as the off-path tech towards monarchy. And sometimes you get these techs, or WC or Writing, from huts or even from AI contacts. I'd guess that getting a second off-path tech mainly to make IRB's easier is not worthwhile. You don't have a lot of gold early in the game, even with maxed taxes, so you can usually spend all you have just on rows 1, 2 and 4 (or whatever rows are available).