You won’t be Abel to use a level.
Could make a 10 degree wedge shaped block, put two levels on it.
you can assemble the vertical and horizontal pipes together with the Tee-clamps
Yes, need pipes lined up. Preferably tops lined up too so they don't need to be cut.
The "horizontal will be several pieces with multiple supports each, so assemble as you go with supports on end of each (aligned by 2x4 and/or straps), then go back and hang any intermediate supports.
if you must follow thw contour, make series sets and stairstep to the slope...
Staircase needs spacing to avoid shadows. Slope in X and Y doesn't.
Similar idea for panel on wall of building under eaves. If pushed out to it starts at edge of eave rather than under eave, avoids shadow moving across it (but more structure required.
Maybe I'm misunderstanding his plan but if I'm not then the all panels will be at the same angle but the whole array will be tilted 10 degrees EW.
Seems like a good plan.
Top bracket with tilt could have been another.
Gravity will want to push the uprights over, but not much at 10 degrees. Diagonals would of course make it rigid.
Any other sideways forces, like wind or earthquake?
The top of the rails can be ran with the slope.
But the supports should be plumb for strength.
Except for his 90 degree "T" brackets.
Ugly trusses would completely take care of strength. Thin cables carrying tension work too, have seen in some pictures here.