when it comes to increasing guitar speed, should you do the same exercises over and over again until you speed them up fully, or have different exercises to do each practice session to increase guitar speed.
don't expect to develop high speed from night to day, also don't stick with the same exercises they to define goals, like getting X Bpm on that exercises that move to another more complicate, etcetcetc.
It's all about developing co-ordination. Your can pick and fret as fast as you like, but it means ****-all if you're not co-ordinated. For specific practice, you play along slowly to a metronome making sure every note is perfect, then eventually turning it up a few ticks. That develops your co-ordination. When you have that, speed is just a matter of pushing yourself and staying co-ordinated.

As to what you play... that's up to you. I like to play songs and melodies in straight sixteenths instead of boring scales.
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You should practice a variety of exercises and have patience for speed to build up. Make up your own exercises if great to do as well. Do not get so distracted with speed though and neglect actually trying to create your own music.