#1
If I have a C Major I IV V chord progression, should I form my lead riff and
solo from a C F or G major scale? Also, what technique do bands use to form
their chord progressions if they do not use the common I IV V? I'm trying to understand the relationship between rythm and lead, and any links to lessons or threads would help.
#2
Well, one approach would be to use the C major scale over the whole progression. Another would be to arpeggiate each chord which means that if you are playing over the C major chords, you would play the notes C, E, or G. You could also use modes and put those in the mix.

And there are other progessions such as:

I-IV-V
I-V
I-IV

I think another one is ii-IV-V-I.