Arrowstorm
Chieftain
I think the important thing for Venice is to grab 2-3 city states as the game progresses. This allows them to use some of their trade routes to send food or hammers between the cities, granting a significant advantage while still maintaining a strong income from the remaining external trade routes.
The first city state can be grabbed via the Merchant from Optics, so thats no problem. The second merchant can either be grabbed via Leaning Tower or an early market specialist. Everything past that does either require more specialists or an early maxed out commerce SP tree.
Lets say you have 3 cities during the rennaisance: With 6 internal naval trade rounds you can send 8-20to each of these cities, allowing you to fill all specialist slots while still using 4+ external routes to make some decent money. After that you can use rationalism to get another +2 science per specialist and freedom to reduce specialist food requirements even further. I think my last game ended with a size 54 capital that had all specialist slots filled + all tiles worked + 2 unassigned citizen.
So, yeah, if you stay too small you will fall behind. But with some well planned city state buyouts you can catch up again pretty quickly.
What exactly do you mean with a well planned city state buyout? Taking it when it has a lot of units in it?
It's looking to me like on high difficulty levels that Vinice is designed to abuse the science leakage from trade routes with double.
Basically if there's any civs ahead of you in technology, you should have as many routes with them as possible (as opposed to routes with those behind in techs)
Playing continents, is it worth taking some city state close to the other continent(s) later in the game, so you can trade with the civs there?
Oligarchy and Aristocrats.
The 'free' MoV at optics is enough to get you started, terrain depending. Then, you can just generate them normally via GPP.
You definitely want at least one puppet early as soon as you can leverage it properly. After that I focused on allies instead because early happiness is crucial. You cant afford to spend early growth turns in unhappiness.
Isn't Aristocrats worth it for securing the wonders? On immortal+, at least?
Also, I see you removed Attila entirely from the game, didn't everybody start hating you?