Athenian, Venus has multiple meanings. In a heterosexual man's chart she shows his ideal female. I think in a gay man's chart, she is more generally the object of his affections. Venus generically rules the fine and performing arts, and the principles of beautify and esthetics. Venus rules luxuries like jewelry as well as activities associated with femininity, like hair-dressing.
Venus shows our capacity to appreciate beauty.
Hmm... so, I think I need to relate my life experience here to explain why I see it as having a negative influence on my life, though I was trying to avoid it mostly because the explanation will be kind of long-winded.
Let's see. I believed I was asexual for most of my life, because in high school people showed me various pictures of both men and women, and neither type of picture actually did anything for me, nor did simply seeing others that most regarded as attractive. It wasn't until age 29 that I figured out this wasn't the case.
At age 29, there was this odd girl. A lot of people got angry at her for cheating on a man who was respected within the community. I wound up kind of feeling bad for the girl, reaching out and trying to comfort her, listen to her side of the story. She wound up telling me about all the hard things she'd been through, as well as all the guys she'd ever been with and the fantasies she'd had, etc. She was in her mid-20s, apparently had not been single since she was 15, and the idea of being alone terrified her. If anything, it seemed like she started to lean on me emotionally a bit due to not having many female friends.
Eventually, this girl fell in love with me and started pushing me to share pictures of myself. At first, I thought it was a joke, but she seemed pretty serious. I was rather surprised because usually women see me as a friend, and I'm generally okay with that... so I wondered if I sent odd signals this time. It turns out, she apparently has a hard time developing an emotional connection with anyone without turning it sexual. After she started acting this way, asking for pictures and pushing to make things sexual/romantic, I fell in love with her.
So, the thing I figured out from this situation is that I assumed I was asexual because I don't have this way of being where I see something attractive, know that I want to possess it, and then chase it and try to do what it takes to get it. That's the way sexuality seems to work for most people. But in my case... it doesn't. Instead, it seems like there are a lot of conditions required for me to feel anything in that department. Like, first I have to feel an emotional connection. Then, the other person has to make me feel somewhat attractive or desirable to them. Third, it really helps a lot if they're very assertive and like to take charge in the department of moving the relationship forwards, kind of seeming like they want to chase me or something. Since she was the only person ever to make all three of those things happen, she was the only one that ever made me feel anything in that way.
Finally, the girl did wind up marrying another guy who lived closer to her. However, she never kept her relationship a secret from me, although she kept talking about marrying me and seemed unsure of what she wanted right up to the last minute. When she got married, I assumed we would stop talking, but that didn't happen. Instead, she told her husband I was gay to ensure he didn't ask her to stop interacting with me. She said I have something of a "gay vibe" and that she was sure he wouldn't suspect anything. Thus, we talk to this day, she complains about her husband to me all the time, like how whenever she asks to be intimate, he has a headache, etc. In the end, I didn't get too angry about this although it did hurt a bit, because I ultimately valued the emotional connection more than the sexual one, and she probably knew that was the case and that I'd be there regardless. She basically said I'm the only person she doesn't feel like she has to hide things from, and also said, somewhat cryptically, that she thanks me for "showing her how to love her husband" at one point, as if her relationship with me taught her what she needed to know to get him interested in her? It was very strange.
So, from my experience, I think it's pretty obvious how the traditional Venus in 12th house signification of secret relationships played out here, as well as how a strong Venus could potentially result in a man being effeminate, as you pointed out the Hellenistic astrologers said.
The reason I see Venus as a somewhat negative influence in my life here is, well... because it is so strongly placed and above the horizon, that I think it is at least partly responsible for cursing me with an extremely atypical way of experiencing and processing the sexual side of life. To be fair, I'm sure Mars being in the 8th house in Capricorn may have also somehow played a role in Venus having such an unbalanced influence here, but I don't know how much of one. The way Venus was described in one of those videos really hit home for me, actually... when it was described as "the light that beckons," draws things into itself, passive, etc.
Because it seems like that's a perfect description of my issues in relationships... on some level, the sexual side of my nature is too passive and wants to draw things into itself, beckoning rather than commanding. And that way of being causes so many problems for me that I thought I was totally asexual for 29 years, because that's how long it took me to find a situation where that type of sexuality can even get activated.