I always see people talk about speed like it's its own skill you can train separately from aim, consistency, and accuracy. Am I the only person who thinks this isn't true? I've always seen speed as a "summary stat" of the other skills. Speed is simply the limit at which you still have solid aim, consistency, and accuracy. If you can't hit squares or stream at 160 BPM, you can't do it at 220 BPM. You might think you can because you occasionally hit patterns in FD or Airman, but more often than not, it ends up being uncontrolled flailing that does just that - occasionally hits patterns. Always learn to do things slowly before you learn to do it quickly. Once you have control, the speed will come. At least, that's what I learned playing piano, and it worked for me.
The only aspects of speed that are independent of control is physical capability (actually being able to move your fingers and hit z/x quickly enough) and endurance, and that comes with practice and time. As I remember Aqo saying in a thread many moons ago, you can only stream a BPM if you can do it indefinitely - hitting short bursts in maps like NNRT doesn't demonstrate proficiency in any way (I can do that no sweat, but I can barely pass Ascension to Heaven, which means I can't stream 200 BPM).
I guess AR is an entirely different debate altogether, but learning AR 10.3+ is irrelevant if you can't play AR9 songs with DT anyway (just because you can read it doesn't mean you can play it). Don't be that beginning guitarist who tries to play Van Halen songs 2 weeks after learning scales.