Let's be serious. Most of the taboos around sex in a western world are long gone. Anal, the forbidden fruit is stuff Grampa talks about around Easter dinner. We turned abusive relationships and BDSM into romantic comedies. **** - The final frontier - is all the rage now, because we did everything else at this point.

What is the blased author to do then? Simply go back to the simpler times! But the modern technology is so friggin convenient no? Steampunk? Well could do that in the future, for sure.

But then I can just create a different world, where the technological progress madly accelerated at some point, but it somehow didn't pull the society into modernity. Where Man are still Man, women are still expected to dress modestly, and shaving pussy is act that even lowest of the lowest whores will find abhorrent. You know, like Saudi Arabia.

Taboos

So - for purpose of this story main characters are much less educated then they would be about sex. Many taboos and superstitions still hold. In particular ones that will be important to the story:

Tanning and especially Tan Lines. Because tanning is associated with hard work in the field, and lowest of classes - tanning is simply not a thing. No-one would willingly lower their social standing by intentionally exposing themselves to the sun. Tan lines are even worse because they can show the difference between natural shade of skin and the degenerated one. So the person with natural olive skin (3 on Fitzpatrick scale) will be higher status, then person who tanned from 1 to 2 on that scale and has tan lines to prove it. (Note: For the purpose of the story, everyone tans exceptionally well, and they do not burn, or only occasionally suffer sun-burns, also skin whitening treatment exist as they do in our world)
Grooming - Most men wear beards, some wear moustache, some both. Clean shaven men exist, but are in minority, pubic hair grooming is super rare.
Women do not do any sort of pubic grooming. Some might do some slight cutting to shorten excessive ones in the comfort of their own home, but trimming, shaping, or shaving are just not a thing. No woman except worst degenerates would be caught dead with a bald cunt.
Pornography - Internet does not exist in a form we know today (cross world), every country controls their own cyberspace with cross-border connections heavily limited and monitored. In the country of interest access to online porno is tightly controlled and access to pornography is very limited. However publications on the level of old playboys/playgirls are available both in paper form and online (so you know, gentleman can buy them for the articles).
Sex Toys - The selection of the off-the shelf toys is extremely limited. You either buy them through friend of a friend (think "Pure Romance" MLM), in shady shops, or order them made for serious cash.
Anal Sex & Oral Sex - Not something a Lady or Gentleman would do (ok, a lot of them would, but they would certainly not talk about it, or admit to it). Some whores offer it at double, or quadruple rates.
BDSM - Mostly available in private clubs. Since slavery is legal, a lots of sadists simply abuses their slaves if they can afford to own one.
Homosexualizm - Ladies and Gentleman do not talk about it. Despite a common occurrences of two "war buddies" living together in single apartment, or two "old maids" spending their lives together for half a decade. You just don't talk about those things in a good company.

Anti-Taboos

While some taboos exist in the world of the story, that are long gone in ours, some of the customs of the world are taboos in ours. What will not surprise our characters are:

Same-sex nudity One thing that is different then our current western culture is the nudity within the same sex, including public places. It's pretty normal for men and women to enjoy the sauna or public baths together completely naked (of course separately).

Enforced Chastity Chastity belts, cages, and perihelia are considered something niche, but acceptable in the world. Some husbands leaving for a war will lock their wives in them. In some cases the reverse happens.