Yeah, I also like thinking "what would the character do in this situation?" rather than just deciding everything immediately. Outlining is very helpful, I agree.
That "what if i did this instead?" is such a good question, honestly! I went back to an old draft that I wrote years ago and played around with an alternate (more logical to my older self) idea of how things may have worked out. I don't think I could naturally pants an entire story like you though, that is impressive.
Ah, that is true. If only there was a way to architecturally design things that grow themselves, haha. It almost feels like two different parts of the mind battling internally.
Plotting like that is certainly efficient. I always wonder about writer's block, because I have not experienced it. Usually it is everything else in life that gets in the way. time just gets eaten up sometimes. Good to know that plotting prevents it, if I ever run into a stalemate with my own imagination
Ah, so the main quest and sub-quest sort of design. That is a good one and I think it works especially well for interactive stories (D&D, video games, etc). I mean, if you didn't have a main questline, it would be sort of chaotic, but your side quests probably make it more exciting and diverse.
More than writer's block as in "I don't know what to write here or how to write this scene" is more like the opposite. My mind gets overwhelmed by all that is left to write and how do I connect it and oh my god I really want to get to this climax point but I need to create a good build-up for it but X and also Y and Z and... I end up not writing anything.
It's more or less like procrastination is many times caused because we get overwhelmed by the size of the task we have ahead. Plotting is my way of taking that huge task and spliting it into smaller, more manageable chunks that don't scare me as much
PLOT
I need the structure in case I can't think of anything. For example I had plotted out the first half of Demon House extensively, and had an idea of all the major episode arcs. I also plotted out the ending extensively. But I had room in the second half for more mini arcs before the endgame would start. I just thought, "ah, I'll think of something when I get there."
Fast-forward almost 4 years and I only came up with one mini-arc TwT
So I was like "welp" and just went into the endgame after that.
Your story might have felt less streamlined if you had taken too much time with sub plots, though. So, perhaps the end result was a really cohesive experience? 
Oh yeah, from the start I never wanted to focus too much on subplots since it was supposed to be an overall light comedy series akin to a tv sitcom that's more episodic.
But I'm glad I didn't come up with extra stuff because after 5 years I was ready for that series to be dooooone.
I plot the world out, roughly outline the story, and pants the dialogue. So I use all of it, but I keep rough outlines so that if something pops into my head that is better than the rough plan, then I use it.
I like to have room for improvisation.
I meticulously plan everything on word documents, school-outline style (headers, sub-headers, bullets, etc)
I only keep the dialogue vague so I can improvise that as I go, but story-wise, I have it all completely down before a chapter gets written.
Exactly! I am a character driven writer and most of my conflicts are internal/ man vs man. This doesn't mean that I don't plan for the universe around them, but I tend to fill those details in after the characters are stable. I also feel a little strange trying to explain my process to others because I feel like I don't make sense XD
I've done both and continue t do so. I was a staff writer for an professional audio drama company for 12 years. The boss would totally plot everything out, I would do both. Of course writing audio drama is strictly dialog (I never used narration) and then I would let conversations take their natural course and edit.
I don't think either method is better than the other. It's totally up to the author and their muse.
This is called architect vs gardener. In my experience though if you don't have some kind of structure it's very noticeable. Even if you don't have all the details you need to have an idea of the shape you want a story to take. Most authors favor one over the other but most use both to some level
I don't know if I'd call it impressive just because pantsing an entire story does come with it's downsides. I probably have a lot more loose ends and threads to nowhere in my first draft than someone who plots out every little detail before writing a word. I'm sure if a developmental editor ever looked at my work they'd probably cry 
Plotting is probably the better way to go for someone who wants to take their writing seriously. I don't know if I'll ever be more than a hobbiest so I don't really have to worry about that too much. I'll usually keep a list of things I want to fix/change as I'm writing if/when I ever do get to the second draft (which I 100% admit only 2 of my books have officially made it to a second draft out of 10 full length novels) but I'll still otherwise go with what my gut says is good for the story at the time. It really is just what feels natural to me.
I tend to do a mixture of both. As a whole, I know what I want to do with my novel, I have the major arcs and themes planned and I know how the story is going to end, but there’s certain details I make up as I go. I have characters with major impact on the story that haven’t even been named yet. Exactly how I’m going to transition from Point A to Point B isn’t always completely fleshed out, and that sometimes gets me into trouble, but I’m constantly experimenting with things so sticking to a plan has never gone too well for me. I’m sure my ADD plays a factor in all this as well lol