The latter is especially unlikely given that most people are limited to 5-7 "items" in their working memory. To design even a simple system, e.g. a brake caliper, that's way more than 7 items, and they aren't "atomic" items either.
Again, this isn't a stab at you, this is a stab at the concept, because it's kind of like people saying they can put on 5lb of muscle a month without roiding. Sets false expectations.
I can’t draw for shit, but I can and do make complex devices and systems with no written plan, just a picture in my head.
Oh, and I’ve put on well over 5lb of muscle this month, by doing brutal hours of manual labour and eating like a horse. Being out of shape but historically stacked makes it a world easier.
https://www.aworkoutroutine.com/steroids-vs-natural/
Maybe you did for one month, after a time of de-training, with all the ideal conditions.
In more general terms, I can see and explore real and imagined environments, and listen to music with perfect fidelity - although doing the hearing bit only works well with considerable focus, and peace and quiet - visual I find easy enough to just ignore what my eyes are seeing, leave walking or whatever on autopilot. To be clear, it’s not like just imagining a thing, it’s more like overriding a sense. When I visualise, I am literally looking at something that isn’t there, when I listen, I hear as though it’s real - although any real noise immediately breaks it.