Regarding a guitar, I think the best advice you can get is, go try some. What works for one person may not work for another. I like blue, you may like green and hate red. I strongly encourage you to go to a local guitar store and try some.
From my experience and I stress MY experience, I find that I like a thin neck. I feel as though I can move around with greater ease. Some folks like a thin neck, some like a big ol fat baseball bat neck.
Regarding speed? It will come in time. For gawds sake, you're 13 years old. You have PLENTY of time. I'm 45, I don't have as much time left here as you do, and I still don't consider speed to be one of my focal points. In fact, speed is on the bottom of the list when I practice. I'm more concerned about accuracy, making chords and notes ring clear and precise.
The goal here is to get the chicks shakkn' that butt with a killer groove, not plugging their ears due to a headache because you playing 20 notes a second with the gain maxed out on your amp WITH a distortion pedal in front of that.
Something to think about. ;)
[U]Ricks Current Mystery Video[/U] - Updated Monday March/02/2015