I have and use open better cities then is only for knowing it just in case but this two mods is compatible? And how? Need patches or something? As far as I understand Open Cities move the cities in the tamriel worldspace then if better cities is loaded before open cities then it can works...or else?

Not compatible. There is a third mod called "Open Better Cities," which brings the cities from Better Cities into the Tamriel world space. It's on Nexus, but I believe it is not supported any longer.

gothemasticator

Open better cities is what I currently use, as I said

My question was purely theorical seeing that "Open better cities" do what "Better Cities" and "Open Cities" should do in sequence, if it works together (and don't)

No. If you do what you describe in your OP, then only the vanilla Open Cities will take effect. The modified closed BC cities will be inaccessible and you'll never see them. I am not actually sure what would happen in the game if you loaded OC before BC since I don't think BC edits the city gates themselves. You may well end up with just OC in either case.

That's why OBC exists. It's the only way to properly transfer BC into the Tamriel worldspace.

You would be correct on both counts, but it is still compatible with the latest version of Better Cities.

Wording needs to be exact here. Open Cities is compatible with Better Cities, but ONLY when not using conflicting parts from each mod. You can use OC Bruma and BC Bravil, but you cannot use OC Bruma and BC Bruma. If you try to use both in the manner suggested by TheNotSoDarkWarrior, then the result will be as Arthmoor described - all cities will be open but vanilla, with only the BC additions placed outside city walls (such as Bravil Docks) appearing.

If TheNotSoDarkWarrior wants Better Cities open, he needs to use Open Better Cities, which is what TheNotSoDarkWarrior is already doing.