What is the benefit/downside of attaching an outpost to a city? Does it just combine the two territories? And is there any way to attach one city to another? I have one that is in a poor location and I want to just add it onto the neighboring territory but can't seem to find how.

There is an attach button right next to the label of the outpost. There you can attach it.

The advantages are that the infrastructure of the city it's attached applies to the administrative center. (an outpost turns into an administrative center once you attach it)

You can build the districts from the city around the administrative center and start planning districts from that general area.

Less management overhead from more cities. The bonusses from the hexes go towards the city it's attached to.

Supposedly there is some kind of influence advantage/disadvantage, but i haven't paid attention to that part when attaching the outpost.

Thank you. Is there any way to demote a city to outpost so I can attach it to another city?

I have only finished one play through, but i have not seen that option. Later on in the early modern age I did get an option to merge cities. but I dont know if that is related to the age, the chosen culture or a tech i researched. Sorry I don't have a clear answer for ya.

The theoretical downside is a stability hit but it seems like it's minor at least at first. I think the question is whether you want to be able to have two places produce two things at the same time. And I guess it's relevant if you're leaning towards the whatever ideology that gives more bonuses to capitals versus cities. And I'm sure there are a million vague/unclear/subtle implications that I can't keep track of related to religion and influence that I don't understand b/c none of it's explained clearly.

It's definetly nice to attach as it saves administrators that You can easily run out of if have too many cities. Yes a stability punishment comes with it of course. So do it at a slow pace and make sure you have some pop in city first and food production. As well as makew sure to add +stablity districts like Wonders and Holy sites asap.

I have played every Civ since the original; Call to Power; Civ Beyond Earth; but this game (ya ya, I know it's still beta) has me REALLY puzzled and perplexed half the time on how things work, and why they work, or why even bother with some mechanics.  I hope it all get's ironed out.

I really like the way the system works currently - it feels like an interesting, smart choice.

Basically, the advantages of keeping them separate are that you can build multiple things at the same time, but the advantage of joining them is that they produce more FIMS, the infrastructure applies to them, you can build more types of districts to take advantage of more land, and most key of all, you can build your unique districts (mostly really strong) one in each territory. Oh, and with closed borders enemies can wander in your territories but not those attached to cities.

I often keep my outposts building artisan quarters to capture all the resources, then join when possible, and especially before going up an era so I can build as many unique districts as I can before they disappear.

Not sure about demoting a city, but you can unattach an outpost and attach it to another. I can certainly see the advantages of absorbing one city to another, though, and it feels historically accurate.