All right, my current game is a failed one but I'm going to play it to the end so I have a better overall grasp of Vox Populi, and can try out things without fear of ruining an already bad game.
Anyway, is the necessity to found a religion in agreement with the "spirit" of the mod ? I thought (and can see, from what I've done so far) that the mod is about removing no-brainers and making every choice interesting. But, if religion is so important that you have to either found one (while not everyone can found a religion) or steal one early on, then your game is decided very early by your handling of religion. And that removes the choice of ignoring religion, it also seriously impacts your early diplomacy (if you cannot get a religion, you have to be a warmonger and steal one). The G&K and BNW approach was "religion is strong if you do it well, if you don't commit to it then you may as well ignore it" ; if I understand correctly, in Vox Populi it is rather "found/steal a religion or face the consequences".
Absolutely not. But if you're not planning on founding a religion you can delay your first shrine way longer, I assumed from his build-order actually including a shrine that he wanted to found a religion, and if you do you probably want the shrine earlier.
That being said, founding a religion definitely helps quite a bit.
By the way, how is the warmonger penalty handled in Vox Populi ? Is it as harsh as in the base game for early wars ?
I don't really remember exactly how harsh the warmonger penalties in vanilla was, haven't played it for ages, but my personal guess would be "no". I can usually get away with eliminating a neighbor without suffering any hate from it.
That being said there are quite a few ways to manipulate warmonger penalties that you should probably know of.
You only suffer 50% of the warmonger penalties towards civs you have a declaration of friendship with when you attack another civ. This means friends are likely to stick with you. I think you got about the same mechanic with civs that are at war with the civ you're fighting, but I'm not sure about that (or if they stack).
If the civ attacks you first (you're not the one declaring war) you suffer significantly less warmonger penalty for taking their cities, as it is seen as justified. This includes situations where you taunt the AI into attacking you by telling him to eff off when he tries to talk to you.
From my experience, the AI seems to be way less likely to get mad at you for taking cities if you're doing well. By that I mean if you're tech-score and military score is high, people tend to turn a blind eye towards your warcrimes.
Cities gained from peace-deals do not increase your warmonger score while cities liberated in peace-deals (You asking for a city that the civ captured from someone else and then choose to liberate it when given the option) still decrease your warmogner score.
EDIT : also, how important are culture guilds ? How many of each do you typically build ?
All of them. Even if I can't afford to work them right at that time, I definitely build them as fast as I can.
A related, more general, question : how specialized are your cities ? With so many flat building bonuses, and so few cumulative bonuses, it seems that specializing cities is not the right way to go - it will just result in high unhappiness if one city is a poor culture-factory, another one is rich but illiterate. That said, is there a point in game where you stop building the same required buildings everywhere, and instead start specializing ? Also, it still seems to be a good idea to build most military stuff in the same high-production place where you have barracks and all, am I right ?
CPP isn't exactly about specialization, you kinda need all buildings (some exceptions) in all cities.
That being said, I usually end up with three types of cities.
First type is the city with a lot of production, it could be a lot of hills or some strong resources. This type of city usually run out of buildings to build leaving it extra time to work on military units and/or wonders.
Considering how important production is in this mod, these cities are extremely useful.
Second type is the high-food city, the high food city is a city with some really strong food-tiles, this could be wheat or deer or citrus/olives but usually it is a coastal city with multiple fish-tiles. These cities can usually end up growing rather quickly, so I tend to exploit that by placing my guilds in these cities, as they can afford expending the extra citizens. Sometimes these cities have fairly low production, and sometimes working all those specialists makes the city fall behind on their buildings, this type of city for that reason is the one I'm most likely to spend money on, investing in buildings (especially buildings that improve production).
Third type is the one that doesn't fit into either of the above categories, they spend most of their time building buildings, never really catching up unless you dump a lot of gold on them or if you fall behind on science. I tend to alternate these cities between growth and working specialists, sometimes trying to get some production focus off if I feel like the city is falling behind (or if I need to get some important building up, like a factory or a seaport)
That being said, these buildings are still an asset to your empire, just keep working those specialists.