drugs & sex?

In my personal opinion, I feel like drug use is a lot more dangerous when left un-moderated and allowed to reach extreme levels. Not every person who uses becomes menacing or problematic. I'm aware this is a very tight moral-rope and people normally choose to shy away from it. Once a pre-adolescent teenager or similar talks about drugs, it stirs the waters and leaves people on edge. Advocacy or romanaticization is inappropriate and essentially enabling as well. But, having an honest discussion about what it's like as long as it's paired with it's harms and dangers seems alright to me.

Now don't get me wrong, I am in no way endorsing the use of drugs.

And I'm willing to change on this one, but I think if a minor ended up buying drugs outside of my control, at the very least I would pray it didn't become problematic.

If we're talking about sex, I think initiating discussions with children is fine. If they asked what the noise last night was all about, saying that you had sex (coupled with a brief age-appropriate explaination) is alright.
Now on a critical note, I think discussions of all the off-chart things you like or anything overly-gratuitus would be unacceptable. Having sex in front of them or talking to them about how much you love S&M is equally unacceptable. 

As they gradually age into their early teens, engaging in discussions about consent, power dynamics & sexual safety is critical. Being open about using protection or similar items is alright (something that I think is heavily dependent on context).

We're better off being open and receptive enough to let a child say something like "oh I had sex with someone" and not be scared completely senseless to even broach the subject. Acknowledge that it exists but avoid really delving into details.

There's nothing wrong with working on building a healthy dialogue with a child and being open about your experiences to a certain extent. Then if the child wants to ask questions or talk about it you have already broken the tension and normalized dialogue.

I'm quite curious what parents think of this approach and how realistic it is. I mean I don't have a teen yet so maybe my opinion on the subject will change when that does.

As far as drug use goes, I don't know. I'm not much of a drug user (as I've talked about before) so I would want to make sure my child has the information necessary to make smart decisions.

If they somehow make it to the age of 60 without knowing what genitals are for beyond urinating, that's on them. If they had questions about something and they asked me, I'd answer them; but I wouldn't go out of my way to expose them to anything; what do I look like, some kind of certified educator?

In all honesty, once my (currently theoretical) offspring are able to fend for themselves; they'd be free to do whatever. If you have the means and necessary faculties to perform those actions, as far as I'm concerned, you're your own person and by virtue of learning to fend for yourself, have earned "the right" to do it if you so wish. If you're not in time for dinner, leftovers are in the fridge and if you get into trouble at any point, well, you're on your own; I've been telling you since you were 7 that if you were going to do anything illegal you shouldn't get caught.

Thankfully, I won't have to deal with this because anyone that sees a potential suitor in me will be promptly driven away by my overall vibe as will any potential adoption agency.

I personally also think doing drugs (including alcohol and cigarettes) around your kids is unacceptable because it makes the likelihood of their eventually using higher. I hate seeing parents drink around their kids. Even if it's just a beer, I think it's selfish. You're essentially letting your kids know there's nothing wrong with it, I know plenty of people who abuse alcohol and do it with their family and in my humble opinion it's a little messed up.

I'll be honest with my kids about how I've experimented in the past, and that I wish I hadn't at all until I was older, more mature, and in a healthier place mentally. 

If my kids did happen to use drugs or have sex before I thought they were ready I wouldn't be livid (or proud either), just remind them about the benefits of waiting. It also helps to give your kids hobbies or motivations to avoid those things.

I have seen what happens when parents take a care-free attitude towards drugs and it's often not great for raising wholesome children. I expect (but not encourage) them to experiment like any young person, but I also expect them to take care of themselves and avoid things that compromise their wellbeing.