In reference to 334.15(C) what is meant by "angles"? If I install a 4/O SER on the face or the studs in a straight line across the studs is this code compliant?
334.15(C) pertains to ceiling joists. If you were to install the wire at an 'angle', meaning not parallel with the joists. Also if you do install the SER on the face of studs, remember they have to be protected from physical damage and they will be compliant. While you are at it you might want to take a look at 320.23.
Parallel to the joist would be a 0 degree angle. Completely perpendicular to the joist would be a 90 degree angle. Anything in between would be an "angle" to the member.