Typically in my games, I keep things structured so that I'm the one primarily introducing story elements, setting the scene, and controlling the actions and dialog of major NPCs. However, I like my players to have a fair deal of freedom so I tend to encourage them to make up and interact with minor inconsequential NPCs (as in, they can't overly affect the plot) and largely deal with their own fight scenes, unless it's against a major character. If I trust a player enough and know they're a good roleplayer who is more interested in telling a story rather than treating it like a game to win, then I even let them have more agency in how they do things and even deciding how a scene plays out. For instance, a player in one of my games killed a named NPC that I had created without consulting me about what he was hoping to do (and usually if somebody has story-related ideas they want to try, I just ask they run it by me first to make sure it's okay) and it was a fantastic and pretty chilling post that did a lot for demonstrating his character's development. I trust his judgement and ability as a player because I've known him for two years and he's always been very reliable. I like to get to that stage with players where they can do things that contribute to the story without me needing to control everything. I rather just tell the story with everyone else and kick things into motion when they need to.
I find it's usually detrimental to a game to add too many tabletop/ video game elements to it unless it's specifically a tabletop game. If people are more worried about stats or their equipment and being able to win, for a lack of a better term, you get really inconsistent writing and people who are afraid to take chances. If you have a character that's shooting at an enemy, I should be able to trust you to know if your character was capable of hitting the enemy or if the enemy would have logically made it to cover. The less I have to worry about micromanaging little systems and every tiny action that happens, the more I can focus on telling a story that the players enjoy and keep it moving at a pretty acceptable pace.
If you get bogged down in the small details and I as a GM have to rule on every action taken, then it takes FOREVER to get through a simple scene and players lose interest. Let's go back to our shootout example from the last paragraph, imagine you have say 5 players in this fight and a bunch of NPCs. Now imagine every time a player describes themselves as doing an action and the GM had to rule on whether or not it worked and write the reactions of each NPC, a gunfight that would have taken like two minutes in real time ends up taking 20 posts to get through and a half a month (or more). Doing things like that is counter-productive and kind of insulting to players, and I am sure it's a huge reason why a lot of games end up failing. If people don't feel invested in the story and are being babysat, they're not going to stick around.
In the hypothetical action scene I set up, it's much better to let players decide if their actions worked or not and you as a GM react with any remaining NPCs that aren't addressed. The only time you should have to step in in this situation is if you think a player's being rather unfair and handling things in an unbelievable manner (such as killing 7 enemies while running around in the open, shooting from the hip and having them piss themselves at his bravado or something without any consequence) or if you believe something is amiss that should be changed, like let's say one of the bad guys throws a grenade, and player defeats the grenade by throwing a backpack over it, believing that it would absorb the denotation without hurting anyone. You explain in the OOC that the grenade would tear through the backpack and the shrapnel would kill anyone within 25 feet, the player edits and carries on. The player didn't know how powerful a grenade actually was, having been raised on Call of Duty logic, and now knows that he needs to find a better solution to dealing with the grenade. While some GMs (Hi Brovo!) are ruthless and would totally punish the player for making a stupid mistake by having Private Ignorance totally get pulped by the detonation in a subsequent post because that's how they like to run their games (and there's certainly a great appeal to them. :D Best reads ever.), a fair deal of GMs probably would rather point out to an otherwise solid player about a potentially fatal mistake because they tend to run their stories more along the lines of a novel where if player deaths happen, it's usually story-related and not an instance of shit luck. It's an exaggerated example, but it should kind of give you an idea of where a GM needs to step in to deal with the details.
Ultimately, how someone GMs is up to them and their own style, be it a micromanager or a devil-may-care attitude, a ruthless rogue-like facilitator of death verses cultivating long-term character arcs. Just keep in mind the more you try to control every aspect of a game, the sooner it's going to unravel.
