I started out with a mouse too, currently I have a tablet with no pen pressure. So my linearts in SAI aren't as fancy as the linearts of the people whose style I love, and it makes me enjoy drawing in SAI a lot less because I don't like the result
Yea, scanners are a pain. Mine tends to randomly crop the stuff I scan into pieces despite having put the options to no autocropping. It's really annoying as sometimes it cuts out pieces that actually had part of the drawing on them, or separates drawings that weren't mean to be apart.