My brother has Venus in Libra/Mars in Sag. But he is getting divorced . It widely conjuncts his Saturn/Pluto respectively.Venus in Libra is in its domicile and therefore quite powerful. But I find that they are more drawn to agreeable "relationship oriented" types than those who are strictly glamorous and/or beautiful.
IME you can be "ordinary looking" with Venus in Libra and they will still be attracted. But what will likely atttact them are personality qualities like kindness ,grace,good communication skills, calmness,quiet and unobtrusive assertion,ability to get along with others and a general "joi de vivre".
Venus in Libra guys are turned off by ill manners or women who are too fiery and prone to temper tantrums etc. Unless Mars aspects Venus/Moon Sun.
This guy is quite passive and would prefer it if their partner was an iron in a velvet glove i.e never show fangs but imply you can bite etc. And they also like to keep options "open" i.e being inlove with more than one person at a timd and being torn between choosing between two(or more) options.
Camilla Parker Bowles was whom Charles was really inlove with. Not the more "beautiful" Diana. He married Diana out of "duty".
Camilla also seems a tenacious and determined personality who was unrelenting in staying in Charle's life even during his marriage to Diana.
In a way, I think this was what continued the attraction to Camilla for Charles. As she was there to "offer" an alternative from what he married. And always keep him romanticizing of the "other" option (even if prohibited)
Prince Harry married a more feisty woman. And that could be because of a sextile aspect between Venus and Mars.Perhaps also his Juno in Virgo squaring natal Uranus in Sag.
I find that there will be plenty to disagree on because his Moon in Taurus is juxtaposed to the woman that he married. I mean the ruler of of his 7th is Moon(Taurus) and it opposes Saturn.
So Harry is quite "matter of fact" and cool emotionally and quite traditional really.And so he expects married life to be an enduring life of "duty" and "service".
The Venus in Libra you spoke about will be evident only on the surface. He is more likely to keep an image of "all is well". But to say that he is a romantic and "heart on sleeve" type?No.
With Libra Venus appearances are everything. So if you are able to smile and keep up appearances, that would be good(even when things are not good).But be warned that most make lazy mates who will expect romance to continue even when they don't put in the work to make it so.
So it the attraction wanes, they will get more and more distracted by the "possibilities" outside and wonder if they have made the "right" choice. This is the."options open" part.
I bet that Harry wonders now and then if he indeed married his true mate(Libra is often preoccupied with that). In his case not so much for romantic purposes, but more for what will last(Moon/Saturn opp). As he prefers the mate to be emotionally self sufficient and not always in need of him to hold their hand(as he can be and will be emotionally unavailable).