At one point I tried to create brushes that matched some stairway models- they had steps that were 4 high and 8 deep, with an identical spacing between them and a 45º rise/run (basically lay down a step, go back 2, up 2, place another, back 2, up 2, place another, etc.), and it works without a hitch.
As for heights, I believe the character models run about 80-something, with 96 being my default as that allows head clearance and also is the minimum height to set up a teleporter. Most of my walls run about 128 to 192 high; that's enough to allow a Scout to double jump and not hit the ceiling. A Scout using a FAN and double-jumping will reach about 204, meaning 256 will give plenty of space in any rooms where you're expecting lots of fighting; if you want to allow sticky jumps and rocket jumps, you'll probably want to put the ceiling up around 768 to 1024 or higher.