I play in the high-stakes NFFC where 3RR is the standard. We also use KDS (Kentucky Derby System) where owners get to submit their preferences of what slot to draft from. These are 14-team leagues so take what I say with that in mind. The NFFC's version of 3RR means the rounds go 1-14, 14-1, 14-1, 1-14, 14-1 and so on.
I can tell you that the 7-9 slots were usually 3 of the last 5 slots of most owners in order of preference.
Many times, most would pick slots 1-4 (depends on where you consider the top tier to stop) then they'd go to the back end of the draft in slots 14-12, then finish with some mixture of the rest of the slots.
Therefore. their KDS ended up looking something like this: 1,2,3,4,5,14,13,12,11,6,10,7,8,9
I think one of the most important things to consider is where, in your opinion, there is a clear dropoff in talent. Let's say you consider the top 40 overall to be pretty clear and then the waters muddy, so to speak. Then let's assume you are in a 12-team league.
That puts the dropoff at about the 4th pick of the 4th round. If I were setting my KDS, I'd go 1,2,3,4 for sure. This would get me 4 of the clear top 40 players on my list.
While 7-9 slots do offer some perceived advantages if people are letting value slide all around you, you can see that in this example, the value goes away quickly in the 4th round as the choices are much less clear.
Same with having the 10th spot or later, once you get past the benefit of the 3RR in the 3rd round, most of the value vanishes as the picks are less clear from that point on.
I hope this makes sense to you?!