You have two options (and hey, they're the ones you mentioned in your question!), and it sort of depends on what exactly you're wanting to do.
First and foremost, most likely the advice I give here is only any good until we see the full NPC creation rules in the DMG where hopefully there will be much easier shorthands than what I'm going to suggest.
The by far and away easiest thing to do is to take the Mage NPC, spell swap for find familiar (something you're given full license to do in the rules, and even if you werent...well you're the DM) and just be done. Also add a racial trait to him to make him feel more like a dwarf.
Your other option is to build up a Wizard as if he was a PC. I'd advise against feats and just take the most basic options and equipment.
The first approach is way easier. You have a set CR, you don't have to rummage for the right spells or anything else really. The cons here are that you don't have any scaling rules for the NPC (he's set at CR 6), and he doesn't necessarily feel enough like a dwarf. These may or may not be problems for you.
The second approach has the pros of being fully scalable, and can be built as a dwarf so it will have a dwarf's racial traits etc. On the flip side, we don't have a PC->CR guide yet so you'll have to guess and it's a ton more work than just pulling up an NPC that's already created.
In a lot of ways what you do probably depends on context. If this is a one-off villain for an encounter, use the pre-gen'd NPC. But if this is a long running villain who is worth more of your time, build him as a PC and maybe even level him with the party.
Given that this character is going to be a quest giver, I'd be inclined to create him with PC rules as the customization offered in that set is going to be far better than what's available for monsters right now (in a month or so, I might change this answer, but I just don't know yet). The only caution is that if you make him too much higher level than the PCs then I wouldn't ever (or maybe only on super rare occasions) let him fight with them. (DM PCs aren't a great idea anyways, though, so there's that)
Make the NPCs a vital part of the story.
Earning Trust
Perhaps the NPC is there for the PCs during tough times. Receiving a "get out of jail free card" once in a while from a prominent NPC can go a long way into the PCs caring. Also, increasing the amount of dialogue and feedback between the PCs and the NPCs also go a long way into developing a relationship.
Coercion
Perhaps there is an effect (curse, magic, hostage, blackmail, etc) in place that forces the PC's to care about the NPCs whether they really care to or not. "This or/for that" can be a very good story arc for the PC's to overcome and interact with. If the PC's make a wrong move toward the NPCs, then disaster can strike at any moment.
Overall Effect
The more you have your NPCs as part of the PCs' lives, they will care about them one way or the other. Have drawbacks that affect the PCs or lack of reward if the NPCs are neglected. Have boosts that affect the PCs or abundance of reward if the NPCs are not neglected.
It will really come down to what you, as the storyteller, give the PCs information and facilitation for a relationship with the NPCs. Whenever you read a novel, you as the reader will either care or not care about the protagonist/antagonist due to the writing style of the author. Your NPCs/PCs will be no different. Think of your roleplaying sessions as a chapter in a story novel you are writing. With that frame of mind, the PC's will flourish in ways you haven't seen them perform yet.
Best Answer
Romantic entanglements are just another character-based plot hook.
You can satisfy your notoriously annoyable player along with the more interested players by keeping this in mind: it doesn't have to be fluff. I've had an NPC romantic entanglement as a player (well, it wasn't all that romantic, but the setup is the same).
Some people really like tons of extra detail that doesn't necessarily touch directly on the main plot (or any plot), frequently because that makes the setting feel richer and more "real" and helps them get into the minds of their characters. Others simply like certain types of story element or subplot, and will enjoy a story that has that sort of thing in it. Still others dislike everything but the most pragmatic, efficient dissemination of story elements and guidance through the plot.
But I've never heard someone, of any player archetype, complain that a story element or subplot was woven too well into the main story or the game overall.
Adding a romantic subplot for a character definitely can feel like something that is apart from the story, and matters only to the character(s) involved as roleplaying/worldbuilding/fluff. That can be a problem from at least two angles:
But, again, things don't have to be that way! Treating the romantic entanglement like any other plot hook, along with prep work to support it, is another way to integrate content some players want to see with the adventure players hope to have and the story that you want to tell.
If the love interest NPC wants to associate with the party just to play the tambourine and pull their significant other away from what the other players want, that's a serious problem. The players exist, and the NPC doesn't. If the NPC is woven integrally into the story in some way that affects all players then it's just another NPC that it's important to interact with, and there can be an extra dimension for certain characters to consider.
Any experience you have with making plot hooks engaging for players is already exactly what you need to tap here, without much modification. Major pitfalls include: