I'm doing a toilet rough-in and have a couple of questions.

1. When looking from above, does it matter which way the waste pipe leaves the toilet? Virtually all installations I've seen show the pipe going out the back of the toilet. But I suspect toilets "fire" straight down, so it shouldn't matter which way the waste pipe leaves the flange. I have to orient mine perpendicular to the toilet.

2. I've seen conflicting advice about how high to mount the flange. Some show it flush with the finished floor. Others show it sitting on top of the finished floor. Why is one method better than another, what's wrong with doing it one way or the other?

3. Lastly, how do you build the 1/4"/ft slope? Are the PVC fittings sloppy enough for the shallow angle? Or is a 90 elbow not really 90 degrees exactly. Otherwise I don't see how build everything slightly sloped.