You can play both with miniatures or narrative combat
Miniature and map combat is supported by the game, but not really encouraged. Coming from a game that is both narrative-heavy and with very strategic combats (Dragon Age), you are allowed to play it however you want.
Take a look at this question about the pros and cons of narrative combat. You will see that the questions that usually come up (Do I have line of sight? I am close enough? Can I get behind him? Can I get cover behind something?) are easily fixed with a battle map and miniatures. But that doesn't mean you are limited to them. If you simply say "yes" whenever they ask those questions and come up with something that feels narratively appropriate, you all will have a great time describing your combat stunts.
For example, when asked if there is cover, and you had not thought about what objects are in the room, come up with something that you would look quickly and try to get yourself behind to get cover, like a table at the corner of the room. It is there now. If asked if the player character is close enough to an enemy, just ask yourself "Did the enemy move? Did the character move? Is there any reason they shouldn't just be able to take a quick step and get close enough to hit him?". The answer will usually be, "If you move a little closer, you are able to attack", which doesn't impede them of doing whatever they had in mind and doesn't slow down combat either. This other question could provide you some useful tips on how to play games with narrative combat as well.
I played D&D 4e with and without maps (and also Dragon Age, for the record), and that's usually the heaviest "map-centric" system usually mentioned when talking about miniatures vs narrative combat. Other than the occasional ability that had a very weird effect, like "hit the target and two other enemies that are 2 squares away", which I simply treated as "hit three enemies close to each other", we had no trouble with it.
But keep in mind that there are players that have a hard time trying to visualize your description without the use of visual aids. Those players usually see combat as a strategy game and like to take advantage of positioning. They will have a harder time, compared to someone who never played a tabletop game, for example, to get used to narrative combat.
So, you have to be very descriptive of the scene, describe relative positions well and allow them to do stuff that in a battle map you probably couldn't due to the limitations of it. For instance, maybe your map didn't have a table for them to jump onto, but if the player asks if there is a table, you should probably add a table to the scene so they can pull whatever narrative trick they have in mind. Maybe there wasn't a chandelier for them to balance on and land on the other side of the room, or maybe there wasn't a tree at the side of the inn for them to hide behind and avoid those arrows shot at them.
The easiest trick is to answer "Yes" more often than you answer "No" during combat scenes. They will get used to it and create the scene with you, instead of reacting to the scene you had created for them.
Stunts add complexity to the combat
Stunts is the mechanic that will add complexity to combats, regardless of using miniatures or narrative combats. Stunts like Skirmish or Staggering Spell, for example, will allow you to reposition combatants and could cause some issues if players are trying to use it as a strategic-positioning ability ("I will move my target between me and my ally so we can flank him").
Skirmish: You can move yourself or the target of your attack 2 yards in any direction for each 1 SP you spend.
Staggering Spell: If the spell does damage, you can move the target 2 yards in any direction for each 1 SP you spend.
But you could simply reword those stunts a little so you don't have to worry about actual positioning. In my experience with the game, that is only a problem during play with maps and miniatures. When I played the game with narrative combat, these stunts weren't very much used other than to get closer quickly, or get away quickly, or to push an enemy away so a mage could blast them away without any risk of hurting the group, which are still pretty good uses of those stunts.
If you are looking for a more authentic view of this, Will Wheaton and his guests on the Tabletop youtube channel played a game of Dragon Age without combat maps and miniatures (part 1 and part 2).