Do any JO or NCAA gymnasts use FIG setting? If so, do they get credit (higher difficulty score rating) when they do so?
No credit. NCAA...it would be very rare (if indeed there is any current competitor who is using it, last season there were a couple girls who were also pursuing elite so I'd assume they were using FIG). There is really no reason to use the FIG setting and in general you don't see it. In fact many will be at one of the widest setting, with the spreader down to the max on the high bar end (there is a little nail/dot thing that stops it...I think that is like 5 below F).
JO..depends. You'll see some "open" competitions with competitors also in the elite system. Or younger girls who are working towards elite. Otherwise, not really. Again, no benefit for an average sized teenage gymnast training for JO and NCAA. It would hold many back from learning skills they would otherwise be physically capable of for no credit or reason. Some of these girls may be "tall" by gymnastics standards. Obviously smaller girls will tend to go on a smaller setting, particularly as release moves come into play.
For international competition there is some benefit to it in that equipment has to be standard. Imagine finding that your bar setting was impossible on equipment in an international competition. And there are also the issues surrounding podium set ups and television and making sure things are set properly. For example AAI super wide is basically the most common in the US now...you can't change the length of the spreader between the bars, you just move it up and down to move the low bar or high bar closer or farther. But when people want to put them really close when they're anchored at the floor (like for a set up in an arena) they tend to lose stability if people want to put them as close as like, the small setting on old uneven bars. Most gyms have anchor...poles (i don't know what you call those things) that are different than how it is set up in a basketball arena or something. Also, anyone who has gone to a competition in 2011 to find out they do NOT have these AAI bars is always in for fun (I realize equipment is generally published with the meet info). I have no idea how to convert those settings to the old kind with the extender. Luckily I've never seen that with optional meets (well actually, seen it at like every high school meet ever...), just gyms that are hosting a compulsory only meet, so I can get close enough and the kids aren't doing release moves or anything.
On the other hand it doesn't seem insurmountable to me to have specifications that had a somewhat greater range and still standardize equipment. Personally to me it doesn't take away from anything at all to be able to change the equipment, like I wouldn't think less of the competition. I also imagine that if FIG standards were relaxed, quite a few gymnasts would take advantage of it and their bars performance would probably be better.
I don't see any reason for the JO/NCAA programs to move to the FIG settings and I don't see that happening. NCAA gymnastics is a VERY high level of gymnastics performance. These are NOT average gymnasts. I am quite certain you could pit top NCAA gymnasts on most events against national teams in other countries (particularly on beam, where I sometimes feel the top NCAA competitors are really awesome in some respects...maybe lacking some difficulty particularly dismount wise but the difficulty on some of the routines is pretty respectable with
rock solid performances - like Grace Taylor - WOW). Whether it's "non FIG" or not, it's incredible to watch some of these meets and I think that's the real spirit of the sport. Most sports have some international variations, I would assume.