I want to add some outlets and/or lights in the crawlspace because I'll be
working in it for a long time, and it would also help future inspection (I
check it once in a while).

I have read past posting about wiring crawlspace and still have some
questions:

(1) Since the crawlspace may be wet, I'd like to use waterproof junction
boxes. Do I also need to put the cables in conduit? Metal or plastic?

(2) Can I tap the power from any convenient junctions I can find, or do I
need to run a separate circuit from the panel? Is there a limit on how many
receptacles one circuit can feed? If I want to install a sump pump, I
remember reading that each motor load of a certain current requires its own
dedicated circuit, is this true? If so, what is the max current pump I can
use that does not require a dedicated circuit?