IMO it comes down to the intent of the member, i.e., what they had in mind (or thought was going to happen) when they originally set their settings to FO+... or AFR, regardless of the NoEmail/SpecialNotices delivery selection. Their "intent", as I interpret it, was that they would receive only messages they manually follow and nothing else (or just SpecialNotices as well). So if one has [either FO, FO+FF, FO+AFR, or FO+FF+AFR selected] and [NoEmail or SpecialNotices], FO should take precedence IMO which means reset their delivery to Individual Messages, because that would achieve the intent (and end result) of receiving only messages/hashtags they manually follow and nothing else. It's also consistent with what the (affected) user would get if they themselves went to their subscription screen and clicked on save, even without changing anything, since the code now checks and resets invalid combos.
In other words, I'd personally err on "giving them more than they thought they'd get" instead of "giving them less (or none) than they thought they'd get". Either way may upset some of those folks, but personally I'd rather have a member be upset/annoyed at me for sending them more email than none at all; they can reset the first scenario because they are aware of it, but they won't know the second one is going on (for a while at least), and judging by the fact that some of us more knowledgeable folks were still fooled, imagine their case.
Another alternative could be to leave things as they are, and send a system email to the affected users only, instructing them to go and check/reset their subscription settings to ensure they are getting what they really meant to get.
Or reset the