Ironically, Voidborn is a very good pick for the Agrarian Idyll + Inward Perfection playstyle.
With Idyll you ideally want only resource districts on planets. But even with Idyll, that won't leave all that much excess housing, so typically you can only use basic buildings.
So you get Habitats to do all the manufactoring (Alloy & CG). And while Habitats are small, their housing district is quite efficient (very important for Idyll empires, since their city districts suck). And with 60 housing you can build a lot of upgraded factories on a habitat.
In fact, Habitats are rather good at producing Alloys & CG (even for normal empires, they are better at it than planets). The main reason people usually don't use them for this purpose is, that Ecumenopoli totally outshine them in this role.
However Agrarian Idyll locks the Ecumenopolis ascension perk. So an Idyll empire does not have that alternative.
On the other hand, Mastery of Nature is actually a bit lackluster as an Idyll empire. Since it only increases planet size but doesn't add deposits, you can only get good use out of it on planets that have more deposits than planet size. And those planets are rare.
Oh wow. Thanks a lot! - So I guess I won't be playing Agrarian Idyll (- and am lucky not to have tried) when I can't use ecumenopolis then!
(Well maybe I'll still try for roleplaying purposes in the future - but I have yet to try a lot of other playthroughs anyways.)
On a side note, I had an idea...
This thread made me look into "resource districts vs city districts" again, and I found something to consider:
Maybe using up ALL the mining districts on my mining worlds / ALL the generator districts on my generator worlds just for the sake of it,
even if it meant building some Paradise Domes (Luxury Residence Upgrades) for lack of housing / population on my smaller worlds
might have been a bad idea(?), and I would be better off converting Paradise Domes to Commerce Megaplexes and make up for the lost housing by converting resource districts to city districts? Or would I really not be better off in the end?
Let's see what happens - replace every Paradise Dome with a Commerce Megaplex: the upkeep is exactly the same, but I get ten extra clerks and one merchant,
once the pops have grown.
All I have to do is make up for the lost housing (7) and the additional housing requirement from jobs (11), by converting some of my normal resource districts to city districts.
How many City Districts do I need? Since at my stage of the game (year 2400 and I'm through with tech and traditions) city districts provide 8 housing but also bring two clerk jobs, the net-positive housing is +6. So I need three city districts providing 3x6=18 net housing to make room for the old and new pops (7+11=18). In other words: I lose 3 resource districts, which is 6 jobs worth around 60 minerals (or energy) but I gain 16 clerks and 1 merchant whose output is 40 trade (and 15 more amenities than I had with the Paradise Dome). (Edit 2: 40 trade here seems to be more like 56-58 as I forgot the "High Stability bonus" (around 20-25% on most of my planets and 20% bonus from Galactic Stock exchange... - man it seems this whole posting ends up moot here! Sorry for all the editing... - but some things I only noticed later)
So I trade 56-60 minerals for 56-58 trade (edit: I had to correct the trade numbers up because of Galactic Stock Exchange 20% bonus and high stability bonus, and minerals down, as my miners only produce 10 on special worlds with world-specific mineral bonus) +15 amenities, which I probably require anyway to keep the 11 additional people happy)
. Edit 2: deleted my astonished swearing, as there no longer is anything to be astonished about...
And all that math was only to compensate for housing: now I also have to provide food and consumer goods for 11 additional people: which at my current policy and species-right settings amounts to around 12.5 food and 2.8 CG - which means I have to employ other people: a farmer and an artisan (well maybe 90% of a farmer and 30% of an artisan - taking into consideration that they themselves will also eat and consume).
(P.S.: my species does not have traits for trade or resource production, so nothing to consider here, and I don't use the "Trade Governor" (+10%) that I can hire from Trade Enclaves, and obviously I'm not getting any trade-bonus from civics etc.).
tl, dr - having paradise domes instead of commerce megaplexes is fine, as long as they allow you to use more of your otherwise unused resource districts by allowing to give up on some number of city districts instead. (Edit 2 - BUT only as long as you are NOT Fanatic Xenophile and otherwise absolutely maximised for trade-boni! - things start to look different in favor of commerce megaplexes then!)
So maybe in my current situation it would be worth going the other way round instead and convert city districts to resource districts on every planet where I have commerce megaplexes that can be converted into Paradise Domes?! - brb: need to overturn my whole plan, cancel constructions, giving new orders the other way round^^
EDIT: Oh WAIT - I have another idea: redesign my species to be "Thrifty" (+25% trade) and consider it all over again...
I guess PDX did a better job with balancing than I thought!?!
EDIT 2:
All the trade boni I can think of:
20% from Galactic Stock Exchange
25% from species being "Thrifty"
10% from Trade Governor (- hire "Expertise" from your friendly Trade Enclave)
20% from Fanatic Xenophile Ethos (- not in this playthrough though because I needed other ethics for inward perfection...)
10% from "Free Traders" civic if you are a Corporation / have Corporate Authority
Putting those numbers from base 40 trade as described earlier you get +8+10+4+8+4=+34=74
Which doesn't sound so bad vs the 56-60 minerals / energy as before. But why stop at counting 6 miner jobs as 56 to 60 minerals, that is by no means the highest you could get it to - that was just the value in my current game - so what's the maximum bonus here?
I have no idea how my miners ended up with producing 9.1-9.8 per miner anyway: base production per miner is 4! So in theory taking away 6 miner jobs should not count as 56-60 less but as 24?? What the F is going on?
All the mineral / energy boni I can think of:
25% from Mineral Purification Hub / Energy Nexus
15% from species being "Industrious" / "Ingenious" - I don't even have that
+1 base for every miner from "Mining Guilds" civic - I don't even have that
...
Wait: I forgot to account for stability bonus, it was applied here for my "10"-miners, but I didn't count it in for my trade-values: depending on the stability value I should have added for example 20-25% also to the trade values I was calculating from base values!
Also: my very head of government is "Industrialist" = +10% minerals; if I had someone that added 10% trade instead it would look even better for my whole "Commercial Megaplexes and City Districts" vs "Paradise Dome and Mining Districts" comparison!
And: I did not mention the "Very Strong" trait you could have - but that now is 5% for all workers, so it also cancels out between miners / technicians / clerks (- but not the merchant, which accounts for 8 of the 40 base value I was calculating with.)
tl, dr after edit 2: This comparison which started at 60 minerals vs 40 trade (before I found my errors and edited everything...) and ended as 56 vs 58 is way more complicated than I thought. (- considering that you could get the trade up to 74+another 8 or 10 for stability it seems my original argument could tip in the other direction towards Commercial Megaplexes very easily in a trade focussed playthrough!