small questions about making a custom slave empire

[Herrius Le Crabe Québécois]

Hello, new player here. I'm beginning to toy with custom empires to have more fun learning the game but i'm at loss about building a custom slaver empire.
Many stuff i read online speak about collectivism being a must but that trait seem to have been removed?
So i decided to look in the creation menu and read the various trait and my take seem to be authoritarian seem a good bet with the slave unrest reduction. And xenophobe state it allow to enslave all alien so i guess that too seem a no brainer?

But i am wondering, if i go xenophobe, isnt it counterproductive to the idea of having alien species working everywhere on my planets?
If i pick syncretic evolution that give a slave specie from the start, will those make my main specie unhappy because of the xenophobe ethic?
I think the only guide talking about utopia slaver faction suggested fanatic authoritarian/spiritualist. Is that is better than my first impression that whisper go fanatic authoritarian/xenophobe?

Xenophobe state it allow to enslave anything, but i fear it may cripple a multi-species empire.
Spiritualist, i don't know what they do but psionic science seem fun, but i loose the ''enslave everyone''. Maybe a mix of the three authoritarian/xenophobe/spiritualist may work? i don't know... building a scientific race was more easy than the despotic galactic slave empire. ^^'

thank in advance for any tips or suggestions.

[Malaficus Shaikan]

Collective has been replaced by authoritarian.

For the max possible slavery you need authoritarian xenophobe.
Authoritarian allows you to use cast system which enslave's minners and farmers(I think) and xenophobe allows you to enslave everything that isnt your own spieces.

Authoritarian allows you to enslave your own spieces aswhile as certian pop by dragging it to a miniral slot.
Where xenophobe only allows the slavery of entire race's.

General speaking slavery isnt worth it.
They produce less then you happy population, cause uprising's and your own pop migh start a free the slaves movement(unlikely as xenophobe's hate allians but possilbe)

If you want to max out your slave empire i found that authoritarian xenophobe militerist is a good combination.

Authoritarian will decrease pop requirement allowing you to spend more on fleets.
Militerist will give you access to full bombardmen which will speed up your conquest of alian worlds.
Which in turn increases your capture of more slaves.

You can have slaves be worked to death, turn into cattle or simply keep them as pets.

I would suggest against a slaver empire tho.
Feeding your ego isnt worth the headache of being the most hated person in the galaxie.