Yea ... no. The monument from the artist enclave throws this analysis out the window.
It doesn't change the relative value between planets and habitats, habitats still don't get the good unity options.
Also, the relevant calculation is whether the amount of unity you can get from a new planet adds a higher percentage of your current income than it adds cost. Which is going to change throughout the game based on your tech level, other traditions, and whether you've met the Artisans or not.
3. I don't know, maybe I just suck at the meta, but I'd almost never (outside of a 1 planet challenge) would consider picking a +4 starbase bonus as an ascension
Most empires will benefit from 144 fleet capacity. Even when you're already quite big it's probably at least 10% of your total. Same with Galactic Force Projection at the point you're likely to pick it, which is third.
The thing this thread doesn't really isolate is what options you have when you pick certain perks.
Your first perk has to be one of these:
Consecrated Worlds
Executive Vigour
Imperial Prerogative
Interstellar Dominion
Mastery of Nature
Nihilistic Acquisition
One Vision
Shared Destiny
Technological Ascendancy
Transcendent Learning
Voidborne
At this point in the game you're probably still expanding unless you've decided on a very tall build, which means that anything that costs influence at this point isn't getting used (that's Mastery of Nature, Consecrated Worlds, and kind of Executive Vigour because you're more likely to spend on expanding than edicts at this point) You probably don't have the leader lifespan to get much use out of Transcendent Learning, or the Star Fortress tech to use Voidborne, and you'll have another slot open by the time you do. You probably don't have vassals yet
either so Shared Destiny is out, Nihilistic Acquisition is terrible and Imperial Prerogative has been irrelevant since we could build on sector planets. And One Vision just isn't terribly useful, it's easy to get loads of other unity bonuses to drown it.
So we're already down to Interstellar Dominion or Technological Ascendancy as your first perk (And even if you did stop expanding you're probably going to take TA not EV first). Even if you take one of these others later (Voidborne, basically) it won't be first.
Second perk only adds:
Enigmatic Engineering
Grasp the Void
First tier Ascension
If you're going for an Ascension you take it here. If you're playing tall you probably take Voidborne because now you do have Star Fortress and you want to start getting into habitat spam if you're going to.
Third perk adds:
Eternal Vigilance
Galactic Force Projection
Machine Worlds
Master Builders
Synthetic Age
World Shaper
Synthetic Age only applies to machines and is unnecessary, Eternal Vigilance is bad because defence platforms are bad, and Machine Worlds and World Shaper both require a tier 4 tech you again probably don't have yet and will have another slot before you do.
So you either take Master Builders
if you took Voidborne second
and have Zero Point Power, take Galactic Force Projection, or go back and fill in an earlier tier pick. Of the earlier tiers you might take Grasp the Void now
but GFP is immediate and costs no minerals rather than taking several years and thousands of minerals, so you can spend the minerals on ships now not later. This would probably be the sweet spot for Executive Vigour, any later and you're likely to have slowed down your influence spend and can keep Production Targets active all the time anyway.
Then your fourth pick is either going to be your second tier Ascension or Galactic Wonders.
From the fifth pick you probably have all the requirements for everything now, so you're picking freely, but the relative benefit of any given perk is now getting smaller. The early tier stuff you left behind is probably too late to make a difference now. Grasp the Void almost certainly still gives you a 10% or better bonus to fleet capacity, World Shaper is 10% global productivity and something to do with all the energy you can't spend, and if you went Megastructures and still want an ascension you pick that for five and six. Either that or if you're in a conquering mood you take your Colossus Project and sack off influence costs forever.