Setting Up Size of Graphics

New to Unity and game development as I come from Android Studio..

I have the worst confusion on game graphics and how Unity works with it and it feels like over a month of research led to very small knowledge. I currently have GIMP as my tool to create characters. I plan on making 2D games and all the tutorials I went through only explains to import sprites from asset store but I would like to create my own. This is where my frustration begins so I decided to find answers here.

I would like my game to not be blurry or set in the wrong position when I launch it on Android and I've seen people do 1024 x 1024 resolutions for their background, characters, and prefabs and just resize the sprite by using the scaling tool or adjusting the camera size. I've also seen some tutorials on the Unity site that they use a quad to hold a background image and that confused me more as some other tutorials didnt. Does this effect the blurriness and can I just create all my graphics (background, character, prefabs) in 1024 x 1024 and just resize it in unity? Any link to tutorials would be helpful. Thanks to whoever could help me with this!