Human World
Sometimes referred to as the Mortal World, or even The Light (versus The Dark).
The games themselves have never made cleart when events take place and dates provided for character births from the original Darkstalkers should be taken with a grain of salt, bearing in mind that it came out hot on the heels of Street Fighter which had a birth year/nationality system which the first Darkstalkers game emulated heavily and was later dropped. Timeframe is further muddled by the otherwise quality OVA Night Warriors: Darkstalkers' Revenge in that it seems to just be an active mishmash of various time periods, technological advancements, and prominent cultures. That said, it's an aesthetic I highly dig and I think it could be very cool to play with.
To put it simply, the human world is Earth - just an alternate Earth. It has all of the same continents, cultures, countries, but is scarcely homogenized. Communications technology, for instance, seem to be very low (the series itself peaked in 1997 for us, so it was fairly far removed from the concept of an "information age" like that which sprung up from Y2K), and as a result many of these cultures are more isolated than we're used to. The benefit of this is that they haven't been trampled or disrupted in the same way as our history, so specific cultural aesthetics were allowed to flourish rather than dampen. There are certain areas of the world that are still industrious and have dense populations, and the cities with the largest number of people seem to be the most advanced when it comes to technology.
Outside of them, technology and style runs the gamut from anywhere between the 12th century and the early 19th century. Even then, certain areas (or rather, specific governments) seem to have access to high tech surveillance equipment and in some capacity televised broadcasts exist, which means recording equipment does too. Vehicular travel seems to be the most contested bit, with steam trains still being a highly popular method of transportation. Cars are available but look no more new than the 1930s models, and seem to be fewer and farther between. Sometimes cars have covered wagons latched behind them, rather than them being pulled by horses or oxen, but horse drawn carriages are also still in wide use depending on the area. Generally, the more populous and wealthy an area the more advanced it seems to be with the most isolated and destitute towns and villages likened to the middle ages. Transport over sea is still often done by sail boats, while for air travel there are blimps but airplanes seem to be limited toward models from the World War II era.
Weapons and entertainment are some of the larger oddities with how widely they differ. Guns and other types of firearms exist but do not seem widely circulated. Imagine if the entire world followed most of Europe's common sense gun laws and America's ridiculousness about them didn't exist. Their makes and models likewise don't tend to exceed beyond the second World War but some exceptions do exist, such as the Uzi (the prototype of which wasn't completed until 1950) and other automatic weapons but hunting rifles and the like seem to be the most accessible. On the other hand, theater and film are definitely available and there are news broadcasts. It would make sense, then, for radio to also be a viable medium and since recording equipment exists I'm willing to say that VCRs along with VHS and other cassette tapes exist. For the shakier forms of tech that can possibly slide, nothing made after 1999 should be used by humans. If something futuristic exists then it should either actually be magitech of some kind from the demon world or it came from a more advanced civilization that is possibly alien in origin.
Aside from that, pretty much every culture that we (as a species) know of can possibly exist. Alternate history stuff is extremely viable (for instance, according to Darkstalkers lore the dinosaurs were actually destroyed by an army of robots created by an alien being 65 million years ago, that were later adopted into ancient Aztec culture). There were some specific countries/locales that were concentrated on, as the earliest release of the game still clung to giving its monster characters human nationalities, and those are: Australia, Brazil, Canada, China, Egypt, England, Germany, Japan, Mexico, Northern Europe, Romania, Scotland, and the United States. Of course there can be more, every nation and culture is valid, but I thought these were good examples for how some things stay the same while others change. Considering the incredible possibilities that come with alternate histories, I would suggest not to tread too far off and leave most things vague; we're all going to try our best to be respectful, so I think the best course is to just keep things vague on the human side of things. We won't be dealing with their politics and histories overly much anyway, just their mythologies and superstitions.
For my own reference, I like to use the birth years provided for certain canon characters in conjunction with their nationality to determine when "in time" that particular country seems to be "stuck", as it were. So for example, Jon Talbain was born in 1940 England, aesthetically I would keep England in the 1940s. The others include: the United States in the 1960s, Scotland in the late 1600s, Australia in the late 1800s/early 1900s, China in the 1700s, Romania in the late 1400s, Brazil in the 1950s, Germany in the 1800s, Canada in the early 1900s, Japan in the 1600s, and so on. However, contemporary vibes, fashion, music, and other forms of entertainment can overlap. For instance, Lord Raptor, a zombie born in 1889, has an aesthetic that encompasses the New Wave of British Heavy Metal despite that only taking hold in the 1970s. Such things should be considered loose, rather than rules, and can be dealt with at your personal discretion. Do whatever makes the most sense for your characters and enjoyment, nothing is really contradictory at this point.