The first archetype that comes to mind is:
Coexistent Primary and Secondary World (both on planet earth):
The writer usually makes up an excuse to explain why the "Muggles" don't know about the fantasy world (like in Harry Potter, Artemis Fowl, The Magicians, ...).
I'm not an expert fantasy reader, therefore I'm asking for a list of possible models to connect the two worlds in urban fantasy. It would be nice to add an example for each archetype.
An interesting model I came across (in the webserial midnight moonlight - not always SFW) postulates that magic means shaping some energy with your intent - and magical rituals and the likes work because people expect them to work, so everybody is constantly emitting intent towards those rituals. Well, everybody who knows about magic contributes to the magical rituals - but far stronger (due to higher numbers) is the belief of most humans that magic does NOT work, and mystical creatures do not exist.
This leads to people who do not believe in magic being protected by what is essentially billions of people constantly casting tiny "Magic and mystical creatures cannot directly affect us" spells. But mystical creatures ARE real, and some of them are rather nasty. So the people "in the know" try their best to avoid having civilians realize that magic IS real, which would make them lose that protection - anyone who gets dragged into the mystical world has to work quickly or get powerful help to build up other protections from the fae and such.
Separation initially due to witch hunting that maintain throughout centuries:
In our world, we have an historic of witch hunting and exterminating different people, so we can imagine real magician would be persecuted worldwide.
If the muggles/magician ratio is favourable to muggles, even with offensive magic, the magician will not be able to take control of muggles society.
Consequently, in order to avoid persecution, magicians will start to hide from muggles, thus creating their secret society. Over time, magicians will gradually improve theirs hiding capacities to the point that muggles are no longer able to find any magician and start thinking they where exterminated.
After that, the existence of magic will slowly change into a myth in Muggles society while magician society keep hiding, convinced that detection by muggles will lead to theirs extermination.
Thereby, we get a society where muggles think that magic isn't real and magician don't want to be discovered and live in an hidden society.
The archetype you mentioned of coexistence worlds is by far the most common one in fantasy literature.
Another one I can think of is where the magical world exits at a certain time. This can be seen in Stig of the Dump, the BFG and other children's literature(Not exactly urban fantasy but they illustrate the concept well enough). Can't think of an example from adult/YA literature right now.
The next one is two different worlds one of which is out own that begin to crossover. In general the two worlds have nothing to do with each other until the story brings them together. Elidor would be an example of this.
The final kind is that the two worlds know each other and the setting is just our world with some fantasy characters chucked in. For this look at some superhero books/films.
Muggles neutralise the power of magic users. Magic users can only use their powers when there's no Muggle around. This is like quantum mechanics where a measurement collapses the wave function. The presence of a Muggle collapses magic. Magic users live in their own communities safe from Muggles and where they work magic effectively. This may explain urban fantasy worlds similar to the Potterverse.
Vampires, werewolves, and other undead apex predators might need to lie low to survive. They usually have powerful weaknesses (garlic, running water and stakes through the heart, silver for werewolves, & salt for zombies etc) making them extremely vulnerable to any systematic counterattack by organised humanity.
Perhaps reality cannot tolerate more than an extremely small number or low density populations of supernatural beings (magicians, vampires, etc etc) in any one place. Too many of them and they self-destruct or competition becomes too strong. The supernatural ecology can't support too many of them.
Fantasy worlds like these are just counterfactual set-ups so supernatural can collide with the contemporary reality. Writers should have fun with that, going too deeply into why of such worlds only exposes their fundamental absurdity. Not that there's any wrong with absurdity.
There's also the underworld model (not specifically referring to the Underworld movies though they are applicable) in which the fantasy beings are either predatory (vampires, werewolves, etc), incompatible with civilised society (ghouls and undead in general) or unwilling to participate in lawful society (fey).
In most stories magic and/or magical creatures are kept hidden from the ordinary word by the government or some other powerful organization (the vampire counsel or the magical congress of America). This done usually for three possible reason.
To prevent a war between normal's and magic user/creatures. If the normal people know about magic they might see those who can use it as a threat, while those with magic our more powerful, but the normal have the numbers.
To prevent a panic: If the government keeps information about potentials terrorist attacks secret because it might cause a panic, why not keep magic secret for the same reason.
To keep magic out of the wrong hands: Magic has the potential to turn anyone into a super weapon. That not something that you want to release to the public.
The Otherworld series by Jasmine Galenorn offers a way for fantasy creatures to come into our world by stating that there are in fact multiple worlds that are very closely tied together at a few points. These are basically gateways that allow people or creatures from one place to pass through to the other side. Over time both sides decided that it would be a good thing to keep track of these portals so that people that have something nasty in mind won't easily pass through and wreak havoc on the other side. This leads to gatekeepers that keep the fantasy population on "our" side in check.
Both sides also realised that there are certain cultural differences, which makes communication very difficult. Modern humans are not known to be nice towards nature spirits for example, so contact is often prohibited or at least very limited. Basically it's just a couple gatekeepers and people-who-don't-really-belong-on-the-other-side that you will find on our side and they keep an eye on evildoers because they like their life here and don't want humans to start a new witch hunt.
You can then either have both sides strictly divided or have them realize that the other side exists and that there can be an advantage to cooperation, depending on whether you want a "unknown creatures of the night" kind of experience or a "new fantasy creatures and how they have always been among us" kind of experience.
