If there is one thing you need to know about planets in the 7th house, is that, more often than not, planets located in this house are energies that we tend to project on other people.
When Pluto is located in the 7th house, the Plutonic energy tend to be disowned, and projected unto others. Typically, we find someone who doesn't feel like they have a lot of power, can feel helpless, or simply "innocent", but repeatedly enter relationships with people who embody darker energies. If this energy is entirely projected, then we'll find someone who repeatedly have relationships where they are submissive, dominated, controlled by their partner. Relationships are very often based on power struggle and push and pull, which can be passionate and intense surely, but also draining and often unhealthy. Sometimes, the person becomes tired and exhausted, and decides to abstain from relationships altogether, but the energy will find a way to sneak back in one way or another.
Sometimes, the person is able to integrate this energy and this is for sure the best case scenario. Pluto in the 7th house means that we tend to project our Pluto energy on relationships, but if you're able to own it regardless, it is much easier to make good use of it. Pluto represents our darker energies, our impulses to destroy, control, and gain power. If you can own this energy, it is easier to make a conscious choice to use it for higher purposes and consciously choose not to control, manipulate your partners.
Pluto in the 7th house is learning how to have soul bonding relationships, filled with devotion and passion, intimacy and powerful love, without falling in the trap of power-based relationships, unequal relationships, and lower energies of control, jealousy, and possession.
The power struggles are a component of pretty much any romantic relationship, but with Pluto in the 7th House - this is particularly potent. I definitely recommend reading "Getting the Love you want" on this subject. You have to remember that Pluto is all about compulsive desire and repulsions, and with Pluto in the house of relationships, the person is driven to be transformed by their relationships with others, yet, are very keen to remain just as is.
More than just romantic relationships though, Pluto in the 7th House has a strong attraction to entering all sorts of relationships and interactions with others, as by comparing the self to others and discovering other people's features, quirks, habits - it is how this Pluto finds a sense of self.
"Pluto an evolutionary journey of the soul": By Jeff Green
"The book of Pluto": Steven Forrest
"The Betrayal bond: Breaking free from exploitative relationships" A book on trauma bond vs love bonds
"Getting the love you want": A book on relationships and notably how to get out of the power struggle