My group is, as far as relationship scores go, mostly in that middling range halfway between 12 and 31 where not much happens. The DCs for increasing relationship scores at each level are getting high enough that even the decently diplomatic characters are failing checks sometimes. Except the Inquisitor. Her class gives her large boosts to intimidate, so she's still effortlessly boosting her relationship scores with everyone every level.
It's not a broken thing or anything, but a little concerning. I expect her to have Ameiko's boon by 11th level, Sandru's by 13th, and all four of them by 15th, in time for the finale. And I'm assuming they don't get any more opportunities for bonus increases like the ones at the end of NoFS (I can't remember if there are any more of those), if there are she'll get to them even quicker.
So how useful are the boons? In this case the ones in question are Ameiko's devotion boon and Sandru, Koya, and Shalelu's enmity boons. How concerned should I be about a PC that's likely going to get all 4 of them?
I would say "almost not at all." Most of the boons, both enmity and devotion, are circumstantial bonuses, often based on class features. Some are pretty strong (Shalelu's enmity is basically favored enemy, and Sandru's is free, stackable Improved Initiative), but even if the players knew in advance what they were I can't see any way that any of them, or even all of them, could break the game.
I would tone down Sandru's enmity bonus, though. Not that it is going to break the game, just that +4 initiative is head and shoulders better than anything else offered.