Well to me, if you open and finish liberty sooner, you get to do some magic stuff with Legalism. The problems I've had, (at least on Deity) was that if you go full on liberty, getting a religion going is fairly tricky unless you play a religion bonus civ.
The hard part is that getting the 8-10 faith quickly can be tricky if you don't open piety quickly, if you don't most of my games by turn 80ish all religions are gone which is just under the time it takes to get Theology and the liberty finisher to get Hagia Sophia. Getting Stonehenge is a complete crapshoot on Deity.
The reason I mention this is that getting Cathedrals in your 3-4 cities is a huge bonus.
So that's one thing to take into consideration.
Other things... Delaying representation by any measure will seriously hurt you unless you are going OCC. It's 145% from base without it on 4 cities, it's 130% from base with it. That's an 11% reduction on 4 cities. Not insignificant.
I'm currently messing about with the Celts and the plan is roughly this, if I don't get swamped and get 4 good cities.
Tradition Opener---> Liberty.
If war might show up early I unlock Oligarchy, if not I try to delay it.
Finish Liberty, either using Collective rule for my 3rd or 4th city (depending on if I needed Oligarchy).
Piety as deep till I get Acoustics.
Legalism for 4 Opera Houses (Ceilidh halls).
Finish Piety.
Tradition till Industrial.
Nuke Freedom, and hopefully homestretch with Patronage and whatever is left in Tradition / Piety.