1. I'd say by the time you open your 3rd SP you should already have 4 cities on French. Price increases quite significally.
2. You need not only opening SP on Liberty as early as possible, but others as well, like 50% of food in storage.
So, IMHO, you should get Liberty first or not get it at all.
It depends a bit whether your want to put more weight onto rapid expansion, or on getting SPs. In the latter case (which I'll go for at least with my first game), you don't want to occur the many-city penalty too early.
However, while I'd like to get in Honor as #2, I realize that I likely won't have the time. I'm a bit torn about collective rule, though. You gain about 4 turns for growing from 1->2 (after which it won't be useful anymore), and I simply don't know how good that is, i.e. how much I'll need to hurry to compete for resources.
Tradition brings a very useful boost, IMHO - you can grow your capital to 4-5 quickly, after which you can start working mines to boost production, or, later, have the possibility to assign a specialist for free.
For city sizes, it's going to be 5/3 till the first luxury resource comes online, then 5/4/2 or 6/3/2 till the second one. Also, if you grow your capital to 9 or more, Legalism gives you enough happiness to found another city. In fact, I'd make Paris a science city, and city #2 (Orleans?) a production city, since Tradition helps me get a capital with huge population fast (note that few large cities seem better for science than many small ones: you get science per population, and each city costs 2 population worth of happiness. Furthermore, there is less building maintenance). Third city might then focus on gold, and fourth on production again.
I think with the French it is important to keep in mind that the culture boost per city doesn't mean that you should get lots of cities to get more culture. If Paris has built Stonehenge and a Monument, the second city will just barely provide 30% additional culture once it has built the monument, and city 4 will only produce 25% additional culture once it gets a monument, and half of that beforehand. Thus, the culture boost merely reduces how much it hurts to get additional cities.
What the culture boost does help with is grabbing tiles. With monuments, you're expanding 100% faster than the competition, with temples everywhere it's still 40%. Especially together with oligarchy you will have a good chance of stealing quite a bit of territory without incurring gold or diplomatic costs.
At any rate, you ideally get in a few SPs before you found your additional cities. Depending on how badly the additional cities end up increasing SP cost (we know there is a factor ~1.3 in there somewhere), it may even be better to go
Scout -> Monument -> Worker -> Stonehenge -> Settler -> Settler -> Great Library
so that you get 4-5 SPs before you build your second city, which means that you can get Tradition, Aristocracy, Liberty and Collective Rule done for sure, and maybe even Honor for defense, or Oligarchy for faster land grabbing.
My dream start would allow me to time the Great Library such that I get Iron Working for free in time for settling city #4 next to a massive iron deposit. Then it would be time to start making puppet states.