NCR Power Armor

The NCR PA is different from others, as it looks like in degraded state from start. The question is - do the limitations (can’t be modded, does not negate falling dmg) come in place after its End is diminished or they are active all the time (which actually makes it ■■■■■■■■■ PA in the game and the only one available to NCR)

All the time. It is just that, it comes into play degraded with that limitations always active. The yellow side means degraded, so you are not going to lose the benefits.

NCR Salvaged Power Armor has no non-degraded profile, so the limitations can only apply to the degraded profile. Additionally, the limitations are active all the time for that card.