I run/have run 7700, 7800, and 7900 downtube shifters by DA, and like any 9 or 10-sp group, you need a rear freehub to hold a cassette, and an RD that plays nice with the shifters. The front being friction, not an issue.
Definitely opens up tons of options and retains the more traditional look.
Range-wise, I've run 53/38 and 11-34. The chain complained at 38/34. I've easily run 53/39 and 11-32, no issues. I believe the longer-cage road RD's (GS models in 9sp and 10sp) are rated at 34t wrap, total. I've exceeded that, but with a noise penalty, and I'm not sure I'd do it day in/day out.
A 9sp setup would use a longer-cage RD, the 6500 GS, 7700 GS, and probably a 5500 GS if they made one. I think Tiagra had a longer-cage 9sp model, too.
10-sp, I've used 6700 GS and 5600 and 5700 GS models. The 105 models (5600/5700) are much easier to source.
If you pair the RD/shifter combo with a compact front, just watch the chain wrap. If you insist on going over the chain wrap rating, I'd recommend you decide at which end of the scale you want issues, the big-big or small-small, and realize you should not be using either, most of the time. The narrow spacing in small/small will create chain rub on the big chainring. The big/big may have that RD stretched out pretty good.
I'm currently converting an Ergo 10-sp setup to Record DT shifters (converted from bar ends) and Chorus aero brake levers. The cost is about the same as Ergos, in my experience, as Campy aero brake levers in good shape, not cheap. But it retains a traditional look, and Campy had plenty of polished or silver 10sp offerings that still look traditional.
I don't get involved in gear spacing. Whatever is offered, I ride it. Easily done, good luck.