I probably should've specified that this whole dilemma only came about because one of my players was quite disappointed with Warlocks' lack of patron interaction during a short campaign we had; so after talking it out with them, I ended up making this thread in an effort to gain insights from the folk here

I've had other warlock players but til now they basically just played them as, and I categorized them in my head as, "different-mechanics sorcerers" (which funny enough is how the 3e class was pitched).. just because I didn't know what to make of them.
I've run two warlocks, three "patrons," of varying interaction with the PC. I'm a firm believer in the warlock class specifically because it's even easier for me to incorporate powerful NPCs, to have more of an excuse than I would for a cleric. A new vehicle to stretch the story in different ways, or a way to introduce further wrinkles and challenges to the otherwise unrelated story.
Warlock 1/Pact A was essentially a "different mechanics sorcerer," in that the patron was not a thinking individual but a battery. Without going into the details of this warlock's introduction after the player's first PC died, the warlock had the souls of many, many murdered individuals bound to them to act as a source of power. This binding was without the warlock's knowledge or consent, and represented power they did not want to keep but you needed someone very, very powerful to unbind these souls.
The roleplay for this "patron" was a tortured warlock seeking true freedom from a cult and what this cult did to them, but also having this source of power that revolted them but the temptation to use it was always too strong. The intent was always to provide a way to deal with that, either by holding onto it but becoming powerful enough to deal with it personally or seeking a new patron to rescue them.
Warlock 1/Pact B was the fae queen of the Court of Winter, one of a few powerful beings that I put around the party to see which the warlock would gravitate towards. I leaned on the book series
Dresden Files, the winter queen uses mortals who swear themselves to her to be her knight. That is not the Pact, the warlock is not strong enough for her to care that much about him. But she will do this kindness, release those murdered souls and replace the horrible sigil of the cult bound to his body and soul with the cold sigil of her court. Binding the warlock to the fae court. And I used this relationship to explain why certain things were happening and give relevant quests.
Like, when a teleportation went so badly that the party was sent so, so far off target as to be anywhere in the world, and took so much damage that it was a near TPK, I had them awake on an island, their teleportation helm broken. As they explored this island, it became evident to the party that the winter queen had reached out and made this happen. She forced the spell to go wrong and broke their means of escape. Why, because this island is where her current Knight is located, where he refuses her commands and acts independently of her. She is very angry with this Knight. Find him. Do not kill him. Give him to her alive, so she can show him just how disappointed in him she is. And then the party can leave, conveniently after a level up where the party could leave of their own power.
Later on, when the party needed to upgrade their power to put them on a level playing field with their villainous target, the warlock's path was to compete against others to become the queen's next Knight.
The winter queen was a dire, severe patron, but the warlock was generally on her side. The relationship was not antagonistic, though it could have been.
Warlock 2/Pact C was antagonistic. Different player, different campaign. Shorter campaign, only a couple years I think. Set in Exandria, the patron was that setting's version of Vecna, before the ascension to godhood. The warlock had an extremely innocent outlook, and had a fascination with the undead and desire to become a lich. This was based on the character's own misunderstanding of heroic stories of powerful wizards. This outlook was capitalized on by the manipulative Vecna, whose motive was to prepare this warlock to become a special kind of spirit jar for Vecna. The end goal was the true death of the warlock, "becoming a lich."
The roleplay was Vecna taking opportunities to whisper deceptions and gaslight the warlock to keep her going under his influence. At a crucial point, when the warlock reaffirmed her loyalty and desire to help this voice, Vecna took her heart and discarded it, replacing it with one of his own. The warlock was tasked with taking this heart to the powerful, but tortured remnant of a champion of several gods, and making him into a vessel for this heart. If she failed, she would remain the vessel herself. I had the voice of one god occasionally try to break through to her, because the warlock was a linchpin in Vecna's plans to ascend to godhood but not be bound by the divine gate inherent to this setting.
Eventually the warlock was able to convey what was happening in the right way to finally trigger the party's interest and concern, and that led to the conclusion of this quest. Powerful arcanists, including a former cultist of Vecna, gathered to sever the connection this warlock had to Vecna. This was ultimately successful, but it left behind one of Vecna's hearts that was within the warlock. I used this to explain that at the end of the day, the power was always the warlock's. The patron had been gaslighting her into thinking he was the source of her power. With Vecna's direct link removed, the heart belonged now to the warlock.
This was a Call of the Netherdeep campaign, that I eventually will use the Vecna campaign as a sequel, with strong TVA vibes as the multi-dimensional connective tissue.