I did it in May 2019, so my information may be out of date. I did a quick Google search and found this, which seems to confirm what you wrote above:
https://www.uscis.gov/sites/default/files/document/policy-manual-updates/20200131-I-130FiledAbroad.pdf
and
https://www.uscis.gov/policy-manual/volume-6-part-b-chapter-3
While the back office procedure looks a bit different, my guess (and it's just a guess) is that it is not going to make much of a difference in practice. The test for what constitutes an exceptional circumstance remains basically the same, and in practice the DOS was making this call as well before (I think they would satisfy themselves that exceptional circumstances existed before asking USCIS if they could proceed under the old system as well). At the end of the day, it was always discretionary, and I'm not sure you could compel the DOS to see things your way. That said, my experience was that the DOS was happy to assist (but maybe I just got lucky).
I remember how stressful this was; for us, we would not have taken the job if we could not make exceptional circumstances route work. In terms of timing, I would start collecting documents now (especially the criminal background checks)...I think 2 months is about the absolute fastest you can get it done; I would count on closer to 3 months.
B