I am also hesitating between concept art and many different things, it's pretty normal to be unsure so don't worry!
As for your sketches, I will begin by saying you're doing a good job on keeping them dynamic which can be very hard. I don't think you're getting too lost on details, and as others have mentionned, your sketches done in 3 minutes tend to look better.
I have noticed that your arms are often a bit too long and sometimes too wide where they're not meant to be, probably because you focus on them and forget the rest of the body when you are detailing them.
It might be better to start with a sort of loose tentacle-ish shape to set the proportions and overall shape, so you don't get lost later when you are trying to define them. Especially if you want to make longer studies of the same poses (which is good to understand anatomy in a different way)!
Maybe take a look at this video if you have the time, I liked this artist's way of explaining his process (he has a lot of other interesting tutorials too):
Hope you found this useful and good luck with your studying! :D
