I stayed in Ennis last year, towards the tail end of your projected stay.
I used Eaton Outfitters, and they were simply fantastic w/ one caveat that I’ll get to in a bit.
We fished the Madison for two days, the Yellowstone for one day, and waded the Ruby on another.
Drifting the Madison and Yellowstone (we never waded) THE fly was a Brown Rubber legs in about a size 8. It’s basically a brown girdle bug with pumpkin silly legs. As a dropper, we used various things but had a lot of success with a Wisconsin pattern that I had brought called a pink squirrel.
On my last afternoon on the Madison, we had tremendous success fishing with Fat Alberts (in about a size 10 or 12).
The wind was up pretty good on the Yellowstone, so we never really got a chance to fish dries.
On the Ruby, the definite go to rig was a yellow sally nymph on the point and a starling & herl on the dropper. The yellow sally would take them on the drift, the S&H would work on the swing.
The one caveat I would have about Eaton Outfitters is that they are licensed to fish the Lower Ruby, but not the Upper. The lower was pretty crowded when I was there, although we got some space and got fish. My guide, illegally, took me to the Upper Ruby (my heart was set on getting a grayling) but there was always a little nervousness there. So if you want to fish the Upper Ruby with a guide, you need to find somebody else besides Eaton Outfitters.
That said, I really don’t think you’d need a guide to do alright on the Upper Ruby. We fished somewhere around Vigilance (?), I think, but there’s a lot of good looking water. When I go back, I’ll hit the Upper Ruby on my own.