Okay this is relatively simple and to the point;

1.) If I am on good terms with the NCR will they get mad at me for wearing there armor? (Like a whole, you have our armor? you must have a killed a guy etc etc etc)

2.) Is there any Legion armor I can wear that won't make the NCR and other guys attack me on sight? (I hate the Legion but I am fond of their armor and would rather not hotkey it every time I stumble on some NCR guys)

1.no
2.not sure about, but I really doubt, although you can wear the helmet

As far as I know anything that says ncr or legion is faction armor so helms generaly never are and certain bondy armors arnt either,

If you're on PC there's plenty of mods that take off the Disguise tag on NCR and Legion armors.

I'd kind of like it if there was a single example of each armour that, say had the insignia burned off or something so it wasn't identifiable as a faction armour. Then you could just wear it as your regular armour (not have friendlies shoot at you), and use faction armour to repair it.