Good to see you got it straightened out. I have seen speeds of up to 240-280mbit DL, at close range on my C7 with LEDE. This with a Netgear A6200 USB adapter which is rated AC1200, on a Win 10 PC, doing a DSLReports test. I'm using it as my home router/AP for the house with 4 people doing various things. Currently running the 17.01.0 release.
So, as you found out, the C7 should go that fast if not a bit faster. Note that this is with no SQM. My cable service is 300/30mbit, but I see peak speeds up to 380, when hooking up directly with ethernet. Update: That, I should say, is equally fast going thru the C7, ethernet to ethernet. The C7 is not yet running out of CPU at that speed.
With the SQM on,the C7 gets CPU/IRQ limited quite a bit lower than that. With limits set for both for DL and UL, I see it getting maxed out delivering about130-135mbit, from a setting cap of 140/27mbit. Running Cake, and piece of cake mostly. Cake is supposed to be less CPU intensive than fc_codel.
Update, the above speed is eth in and eth out of the C7 with SQM on, I should report that using the 5Ghz wifi link, the saturation limit goes down to 100-120mbit. Seems that managing the wifi link takes some extra CPU resources. It will run at 130mbit, heck it will actually deliver about 220, but it's well into 0% idle time above 120, and I don't know how well Cake is doing it's job at that point.
In my case, I seem to have a pretty lag free DL, so I can run with the speed caps set to 0/27mbit, only controlling the UL, and that seems to work pretty well for me. I then get 220-240mbit downloading on the 5Ghz wifi link, seemingly a bit smoother, while the UL lag stays very flat. The IRQ/CPU load stays below100% downloading. YMMV... but that seems to be about where the limits of a C7 are.