The main issue is how tech hungry the start is, especially if you consider settling an S-tier city as your second (and why wouldn't you ? There is no such thing as "too rich". Just stagnate on workers while you wait on your happy cap to rise, if you're worried about it).
Going Bronze into AH wastes a lot of much needed commerce. Inserting The Wheel in between is my way to be "commerce conscious", as you put it. Pottery, I will maintain, is premature, unless you're postponing AH until after the Alpha trade.
Now, The Wheel means that St Petersburg expands borders before AH is researched. Novgorod is also settled before Fishing is researched (Wheel -> AH gives faster Fishing than the reverse). Sharing the corn and then the wheat from Moscow means the capital city has some awkward growth timings.
As far as sequencing goes, I regard my T54 screenshot as a key point to respect maintenance hits. And, contrary to other people's beliefs, I do not think this is difficulty dependent. I would do the same on Monarch difficulty (except I would research Maths, Priesthood, CoL and attempt to Oracle Civil Service).
So, you're right that the copper auto-connect is actually a handicap, here. I did with 2 warriors for the longest time, started Barracks when I thought I couldn't complete a unit.
T54, my 2nd warrior is coming back to garrison Moscow. I also have 19 hammers into an Axe in St Petersburg but, in the end, I let the hammers go to waste as the city shifted from workers/settlers to infrastructure.
Eventually, I traded the copper for gold with some AI (Joao ?) and that let me build a couple more warriors with the horses from Novgorod.
As far as "the North" goes, you may very well be right that the area is best used to place as many cities as possible. With a block against Willem and Code of Laws in sight, it might be better to have a higher global happy cap and better production for the first war. It certainly makes sense if you're worried about production. It's also true that my setup would likely reach a plateau before yours (unless I could steal some jungle from Willem... because I'd not placed my cities so close together...).
Otherwise, once you have the happy cap (we do), it is cheaper and easier to set up a single city, not only for tile improvements but also for infrastructure (forests being a limited resource and being dumped into infra, for example). Having some "super cities" also make it easier to contemplate builds like National Wonders. Being CRE and having dyes, the Globe Theatre isn't entirely out of question in my Yaroslav, nor is the Heroic Epic.
I have a tendency to over-value research over production and to consider science victory conditions (meaning Universities). So, I myself will take my opinion on this matter with a grain of salt. I'm much more confident about the first 4 cities.
I would never backfill south of Moscow once the city has reached size 10+. At T95, I have 3 helpers and Moscow is almost "running out of tiles" (4 more green tiles to cottage). I could consider backfilling in the north, like 3S and/or 3N of Yekaterinburg. Granary, Lighthouse, Barracks, go. As it is, an extra city in the south would likely steal tiles from more valuable cities.
Fair enough @your tech path after Civil Service. In some part it depends on what the AIs are doing and Philo can certainly make sense (I read about your 250 AD GA and 400 AD Lib, and that makes for a convincing argument).
Edit : Looking back and thinking on it (but not doing the simple maths) :
There's a non zero chance I made a mistake borrowing the copper with Rostov to build a 5 turns workboat at size 1.
The city might just as well grow on floodplains, floodplains (same food output as size 1 clams), then borrow the copper at size 3. It's probably relatively close as far as Rostov's development goes but it would certainly translate in a higher output from St Petersburg.
Edit 2 : It is, in fact, a clear mistake on my part, since size 2 Rostov can actually work floodplains, cows. Oh, the virtues of looking back.