Flex lines come off of a washer hookup, through filters, then run to the rooms. More like 'permanent' hoses vs running it to a sink or something. The existing copper pipes (for grounding) is still in place. Denver works under the 2006 International Building Codes and it seems PEX is 'allowed', just don't know the specifics. Seems if you were going to replace the entire system with PEX, you need a grounded 'water take off' installed on a garage wall, but extending a line is different (how much different than if you were to add an icemaker to your fridge, I don't know).
My romex is run along the walls, stapled at the proper distances, but it is outside the walls, not within.
How 'near' water sources? I've got some strips that are wall mounted near the res's for pumps, dosers, etc. Not like they are going to fall in to the res or something, but definitely not GFCI like whats in a bathroom/kitchen outlet in close proximity to a sink.
All wiring is above my waist, water stays below my waist. Nothing is run on the floor or anything dumb like that.