Thank you! :) I'm not sure which one you're referring to when your say "middle one" but I think the 4th picture?
1,4,6 = iPad
2,3 = Note 8.0 tablet
6 = Note 9 phone
The device I'm using plays a role in what I decide to draw, in the sense that I know I can't create very complicated, high resolution pieces on my relatively small phone (theoretically I could but it would take ages and a lot of zooming in and out, definitely not worth it.) The software I'm using also plays a role. I decided to only upload my monochrome pieces since I prefer them and they're more unique, but sometimes I draw in color as well. If I wanna do color, then I'm not gonna use the Adobe Illustrator app for example (the one I love using for monochrome, line based drawings) because it's a vector drawing app, meaning you can't do much with color. So if you don't know in advance what kind of drawing you wanna make, the software could shape your decision.
EDIT: forgot to mention that the 3rd one is based on a very intense song I love, so that's where it's getting the energy from :) I wanted it to look really strong.