Ok so I found the t-51b from the dead bos paladin in the crater by hidden valley and I got the t-45d armor and helmet in the dead wind cavern. They both require training but I thought one of them didn't so where is the PA that doesn't require training? My other question is what's the difference between the two? Do they even look different? Since I can't wear them I can't tell. Thanks in advance.

NCR Power Armour doesn't require training, you can get it from NCR Heavy Troopers, they usally spawn at Hoover Dam.

Is it level dependent or dependent on how far you arte in the main quest?